Chronic paronychia in cats with patellar fracture and dental anomaly syndrome

Abstract

Case series summary

The aim of this case series was to describe the clinical features and treatment of paronychia in cats diagnosed with patellar fracture and dental anomaly syndrome (PADS). Clinical records, photographs, microbiology, cytology and histopathology reports were collected, and follow-up was obtained. Five cats with paronychia were included. All five cats had multiple digits of multiple limbs affected and eventually underwent amputation of the third phalanx of one or multiple digits. A total of 36 digits were affected, 17% (n = 6/36) resolved with medical management and 83% (n = 30/36) were eventually treated successfully by amputation. The cats had treatment with numerous courses of antibiotics (range 7–20; mean 11 courses) over periods of time ranging from 10 to 67 months (mean 32 months).

Relevance and novel information

Chronic paronychia may be an additional clinical feature of PADS and the probable mechanism involves poor integrity of osteopetrotic bone, loss of normal nailbed anatomy and secondary osteomyelitis of the distal phalanx. Medical management with antibiotics, anti-inflammatory therapy and steroid treatment may improve the clinical signs in the short term; however, in severe instances, amputation of the third phalanx of the affected digit seems to be necessary to resolve repeated recurrences and discomfort. Additional information on the long-term outcome is required. In any cat with atraumatic patellar fractures and/or retained deciduous teeth, paronychia may require surgical management if medical management is unsuccessful.

Keywords

Patellar fracture persistent deciduous teeth osteomyelitis osteopetrosis paronychia

Introduction

Patellar fracture and dental anomaly syndrome (PADS) is a phrase that has been coined to help describe cats with the common features of patellar fractures and, in most cases, additional dental anomalies.^1,2 These cats commonly present at a mean age of 28 months when they sustain their first patellar fracture. In more than 50%, a fracture of the contralateral patella occurs with a mean gap of 3 months.³ Other abnormalities have been noted, such as persistent deciduous teeth and/or unerupted permanent teeth, and mandibular and maxillary abnormalities, such as abscesses and osteomyelitis.^2,4 In nearly half of affected cats, additional fractures to other bones and humeral intercondylar fissures occur.^1–3,5 Furthermore, in our experience, a small number of cats affected by PADS develop persistent and recurrent paronychia.

Paronychia is an inflammation of the folds of tissue surrounding the nail. This can be associated with digit swelling, discomfort and/or lameness.^6,7 One or multiple digits of one or multiple limbs can be affected. The two most common presentations of paronychia in cats are exudation with crusting and pedal pruritus with waxy exudate.⁸ Feline paronychia is not common. It has been reported to be an extension of a primary skin disease or secondary to hyperadrenocorticism or neoplasia.⁹ The primary skin disease could include bacterial dermatitis, dermatophytosis and pemphigus foliaceus located in one or multiple nailbeds.^8,10 Depending on geographical location, notoedric mite infestation is reported as a causative agent.^8,11 Primary pulmonary neoplasia or local squamous cell carcinoma are neoplastic diseases associated with paronychia in the cat.^12,13

Establishing the cause and treating feline paronychia can be challenging.^6,7,13 It is important to be aware of the causes of paronychia to be able to provide appropriate treatment for affected cats. Amputation of digits is invasive but sometimes necessary for diagnosis and treatment of feline digit disease. The aim of this case series is to report on the clinical and histological and radiographical features of paronychia in cats with PADS and their treatment outcome.

Case series description

Cats with a history of paronychia and patellar fractures were recruited from the database of cats with PADS; case information on affected cats has been collected since 2005 (SL-H). Cases in the database included cats with the following clinical features: transverse patellar fractures with or without dental anomalies (including persistent deciduous teeth and unerupted adult teeth) and with or without atraumatic fractures to other bones. Of the cases identified, all information submitted to the database was collated and further case follow-up was performed. Where available, records of clinical history, pictures of paronychia, radiographs and microbiology and histopathology reports were included. The database had a total of 218 cats (August 2020), seven of which had paronychia recorded. Two cats were excluded owing to insufficient information. The results and treatments for five affected cats are summarised in Tables 1 and 2, and given in more detail on a case-by-case basis. A total of 36 digits were affected, 17% (n = 6/36) resolved with medical management and 83% (n = 30/36) were eventually treated successfully by amputation. The cats had treatment with numerous courses of antibiotics (range 7–20; mean 11 courses) over periods of time ranging from 10 to 67 months (mean 32 months). Follow-up was performed by contacting owners and veterinarians; mean follow-up time was 41 months.

Table 1

Summary of presentation of patellar fracture and dental anomaly syndrome per case

Case and corresponding number*	Sex	Breed	Bilateral patellar fracture	Retained teeth	Other non-traumatic fractures	Paronychia
1: number 51	FN	DSH	Y	Y	None reported	Y
2: number 83	FN	DSH	Y	Y	None reported	Y
3: number 104	FN	DSH	Y	Y	Light-sided tibial fractures Left-sided condylar fracture	Y
4: number 210	FN	DSH	Y	Y	Left accessory carpal bone avulsion fracture	Y
5: number 215	MN	DSH	Y	Y	Right tibia fracture	Y

Corresponding number in the ‘Patellar fracture and dental anomaly database’

FN = female neutered; DSH = domestic shorthair; MN = male neutered; Y = yes

Table 2

Summary of investigations and treatment per case

Case and corresponding number*	Limbs affected	Mean treatment time (months)	Number of antibiotic courses	Amputation P3 digits	Amputation outcome	Recurrence of paronychia	Follow-up (months)
1: number 51	LH RH	67	8 (on 8 occasions)	LH D2	Healed	No	29
2: number 83	LF RF	10	10 (on 7 occasions)	LF D1 D2 D5 RF D1	Healed	No	72
3: number 104	LF RF LH	46	20 (on 18 occasions)	LF D3 D4 RF D3 D4	Healed	No	4
4: number 210	LF RF	14	9 (on 7 occasions)	All digits LF RF	Healed	No	5
5: number 215	LF RF LH RH	21	7 (on 7 occasions)	All digits LF RF LH RH	Healed	No	96

Corresponding number in the ‘Patellar fracture and dental anomaly database’

P3 = third phalanx; LH = left hindlimb; RH = right hindlimb; D = digit; LF = left forelimb; RF = right forelimb

Case 1

An 18-month-old neutered female domestic shorthair (DSH) cat (number 51 in the ‘Patellar fracture and dental anomaly database’) located in the UK, presented with left hindlimb lameness (case 8 in a previous study).⁴ Radiographs revealed bilateral patellar fractures, and multiple persistent deciduous teeth were noted on clinical examination. At approximately 3 years of age, paronychia was first noted to the left hindlimb (digit unknown). The paronychia initially resolved with empirical systemic antibiotic treatment. Over the course of 5 years, multiple episodes of paronychia of the toes on the right and left hindlimbs occurred. For treatment details, see Table 3 and Figure 1. The paronychia only affected the hindlimbs and a total of eight antibiotic courses were prescribed. Paronychia of digit 4 of the right hindlimb resolved with medical management. At 8 years of age the cat was markedly affected by paronychia of digit 2 on the left hindlimb. Radiographs showed soft tissue swelling adjacent to the affected digit. Culture and sensitivity were performed. As there was no improvement on symptomatic treatment, the affected digit was amputated. At the time of writing, 29 months later, no further paronychia had occurred. The cat was well in itself, despite chronic osteomyelitis of the mandible with a persistent draining tract sinus, associated with unerupted teeth.

Table 3

Detailed description of paronychia treatment of case 1, patient number 51

Age	Digits affected		Culture and sensitivity		Medical and/or surgical management			Improvement
Age	Location	Description	Performed	Growth	Antibiotics	Other treatment	Treatment length	Improvement
3 years 0 months	LH D?	Nail absent	N	NA	Cefovecin 8 mg/kg SC	NA	Once	No
3 years 2 months	LH D?	NA	N	NA	Clindamycin 15 mg/kg PO q12h	Dressing applied	10 days	Resolved
4 years 11 months	RH D?	Nail imbedded into skin	N	NA	Clindamycin 5 mg/kg PO q12h	Dressing applied	14 days	Resolved
6 years 0 months	RH D4	Swollen digit	N	NA	Cefovecin 8 mg/kg SC	Meloxicam	14 days	Resolved
6 years 4 months	RH D4	Nail imbedded into skin	N	NA	Amoxicillin–clavulanic acid 14 mg/kg PO q12h	Two-monthly nail clips	7 days	Resolved
8 years 4 months	LH D2	NA	N	NA	Clindamycin 11 mg/kg PO q12h	NA	5 days	Resolved
8 years 6 months	LH D2	Swollen and painful	N	NA	Cefovecin 8 mg/kg SC	Meloxicam Chlorhexidine wash daily	14 days	No
8 years 7 months	LH D2	Swollen and painful	Y	?	Amoxicillin–clavulanic acid 14 mg/kg PO q12h	NA	10 days	Mild
8 years 7 months	LH D2	LH D2 swollen and exudate	N	NA	NA	Amputation P3 LH D2	NA	Wound healed well

LH = left hindlimb; D = digit; N = no; NA = not applicable; Y = yes; RH = right hindlimb; ? = unknown; P3 = third phalanx

Figure 1

Digits affected by paronychia in case 1, patient number 51: RF = right forelimb; LF = left forelimb; RH = right hindlimb; LH = left hindlimb; black = not affected; dark grey = amputated; light grey = resolved with medical management

Case 2

A neutered female DSH cat, located in the UK (number 83 in the database), presented at 1 year of age for recurrent nailbed infections, specifically digit 1 on both forelimbs. Ten antibiotic courses were prescribed on seven different occasions over the course of 10 months. A total of four digits were affected on both thoracic limbs. Empirical and culture-based (performed twice) antibiotic treatment did not resolve the paronychia. The cat was referred to a dermatologist and topical treatment was started. Further treatments were performed by the general practitioner. Owing to discomfort, amputation of the third phalanx (P3) of digit one of both forelimbs, and digits two and five of the right forelimb were performed within the year (Figure 2). Based on medical records, histopathology indicated osteomyelitis. All wounds healed well, and no further paronychia occurred over the following 4 years. At approximately 4 years of age, the cat fractured both patellae, despite being an indoor cat. The last follow-up was at age 6 years; no further paronychia had occurred. For treatment details, see Figure 3 and Table 4.

Figure 2

Case 2. (a) Severe paronychia noted on right forelimb digit 2. Local swelling, alopecia, ulceration and serosanguinous discharge is noted. (b) Post-amputation of third phalanx of right forelimb digit 2

Figure 3

Digits affected by paronychia in case 2, patient number 83. RF = right forelimb; LF = left forelimb; RH = right hindlimb; LH = left hindlimb; black = not affected; dark grey = amputated

Table 4

Detailed description of paronychia treatment of case 2, patient number 83

Age	Digits affected		Culture and sensitivity		Medical and/or surgical management			Improvement
Age	Location	Description	Performed	Growth	Antibiotics	Other treatment	Treatment length	Improvement
1 year 1 month	LF D1 RF D1	Swelling and infection around nails	N	NA	Cefovecin 8 mg/kg SC	Meloxicam 0.1 mg/kg SC	Repeated 14 days later	No
1 year 2 months	LF D1 RF D1	NA	N	NA	NA	Amputation P3 LF D1 and RF D1	NA	Wound healed well
1 year 6 months	RF D2	NA	N	NA	Cefovecin 8 mg/kg SC	Meloxicam 0.1 mg/kg SC	Once	No
1 year 7 months	RF D2	NA	Y	Coliform and mixed anaerobes	Metronidazole 10 mg/kg PO q12h	NA	14 days	Resolved
1 year 8 months	RF D2	NA	N	NA	Cefovecin 8 mg/kg SC Metronidazole 10 mg/kg PO q12h	NA	14 days	Mild improvement
1 year 8 months	RF D2	NA	N	NA	Cefovecin 8 mg/kg SC Metronidazole 10 mg/kg PO q12h	Referral to dermatologist – topical treatment (?) started	14 days	Mild improvement
2 years 0 months	RF D2 D5	Inflamed and infected nailbeds; D5 missing nail	N	NA	Cefovecin 8 mg/kg SC Metronidazole 10 mg/kg PO q12h	Amputation P3 RF D5 Histology: osteomyelitis	14 days	Wound healed well
2 years 1 month	RF D2	Inflamed	Y	Coliform Enterococcus species	Metronidazole 10 mg/kg PO q12h	NA	28 days	No improvement
2 years 2 months	RF D2	Inflamed	N	NA	NA	Amputation P3 RF D2	NA	Wound healed well

LF = left forelimb; D = digit; RF = right forelimb; N = no; NA = not applicable; Y = yes; ? = unknown; P3 = third phalanx

Case 3

A neutered female DSH cat, located in the UK (number 104 in the database), presented at approximately 4 years of age for paronychia of digit one of the left forelimb and the left hindlimb (digit unknown). It was medically managed for 4 years with empirical and culture-based (performed five times) antibiotics and topical treatments. For treatment details, see Figure 4 and Table 5. Twenty antibiotic treatments were prescribed on 18 occasions. Treatments were sometimes successful; however, relapse of paronychia was common. While under treatment, the cat sustained bilateral patellar, right tibial and right lateral humeral condylar fractures. A CT scan showed multiple unerupted and retained teeth. Three limbs were intermittently affected, leaving the right hindlimb unaffected. A total of nine digits were affected, with five resolving with medical management. At 7 and 8 years of age, P3 of digits 3 and 4 of the right and subsequently the left forelimb were amputated for chronic paronychia (Figures 5 and 6). Two distal phalanges were evaluated histologically. The bones showed large amounts of retained cartilage, which was interpreted as retained primary spongiosa, and one phalanx was necrotic and heavily colonised by bacteria (Figures 7 and 8). The other phalanx had suppurative inflammation replacing the keratin claw and osteomyelitis of the palmar aspect of the ungulate process (not shown). At the time of writing, 4 months after amputation, the wounds had healed well and there was no recurrence of clinical signs.

Figure 4

Digits affected by paronychia in case 3, patient number 104. RF = right forelimb; LF = left forelimb; RH = right hindlimb; LH = left hindlimb; black = not affected; dark grey = amputated; light grey = resolved with medical management

Table 5

Detailed description of paronychia treatment of case 3, patient number 104

Age	Digits affected		Culture and sensitivity		Medical and/or surgical management			Improvement
	Location	Description according to notes	Performed	Growth	Antibiotics	Other treatment	Treatment length	Improvement
4 years 1 month	LF D1 LH ?	LF D1 nail deformed, and necrosis of tissue nailbed	N	NA	Amoxicillin–clavulanic acid 14 mg/kg PO q12h	Chlorhexidine wash daily	7 days	No
4 years 1 month	LF D1 LH ?	RH D? nail sent for culture	Y	?	Amoxicillin–clavulanic acid 14 mg/kg PO q12h Metronidazole 7 mg/kg q12h PO	NA	10 days	No
4 years 1 month	LF D5 RF D1 LH D3	LF D5 nail missing and scabbed RF D1 deformed nail LH D3 inflammation	N	NA	Amoxicillin–clavulanic acid 14 mg/kg PO q12h Metronidazole 7 mg/kg q12h PO	Meloxicam PO q24h	14 days	No
4 years 3 months		Bilateral patellar fractures				Referral for treatment to orthopaedic specialist
4 years 5 months		Right tibial fracture				Referral for treatment to orthopaedic specialist
4 years 6 months	RF D3	Infection on digit; all nails long	N	NA	Clindamycin 7 mg/kg PO q12h	NA	14 days	Resolved
5 years 0 months	?	?	N	NA	Clindamycin 7 mg/kg PO q12h	NA	14 days	No
5 years 1 month	LH D3	Partially lifted off nail	N	NA	Clindamycin 7 mg/kg PO q12h	Chlorhexidine wash dailyMeloxicam PO q24h	14 days	Resolved
5 years 6 months	RF D3 D4	?	N	NA	Clindamycin 7 mg/kg PO q12h	NA	14 days	Mild improvement
5 years 7 months	RF D3 D4	Inflammation, wound between D3 and D4	N	NA	Amoxicillin–clavulanic acid14 mg/kg PO q12h	Topical fusidic acid ointment (Isaderm; Dechra)	7 days	Mild improvement
5 years 8 months	RF D4	Missing nail and small open wound between D3 and D4	Y	Staphylococcus species	Amoxicillin–clavulanic acid14 mg/kg PO q12h	Chlorhexidine wash daily	3 months	Marked improvement
5 years 11 months	RF D4	Mucopurulent discharge; wound between D3 and D4 healed	Y	Bacteria unknown, sensitive to cephalexin	Cephalexin 14 mg/kg PO q12h	NA	4 weeks	Initial improvement; followed by relapse
6 years 0 months	RF D2	Mucopurulent discharge	N	NA	NA	Chlorhexidine wash dailyTopical barrier ointment daily	?	Resolved
6 years 2 months	LF D?LH D?	Infection and nails missing	N	NA	Cephalexin 14 mg/kg PO q12h	Chlorhexidine wash dailyTopical barrier ointment daily	28 days	Resolved
6 years 6 months	RF D3 D4	Inflammation; D3 nail missing; D4 nail ingrown	N	NA	Cephalexin 14 mg/kg PO q12h	NA	28 days	Mild improvement
6 years 8 months	RF D3 D4	Inflamed and mucopurulent discharge	Y	Enterococcus faecalis Escherichia coli	Amoxicillin–clavulanic acid14 mg/kg PO q12h	NA	21 days	No
6 years 9 months	RF D3 D4	Nails missing, inflammation	N	NA	Amoxicillin–clavulanic acid14 mg/kg PO q12h	Chlorhexidine wash daily	21 days	Marked improvement
6 years 9 months	RF D3 D4	Improvement, still inflammation	N	NA	Amoxicillin–clavulanic acid14 mg/kg PO q12h	Chlorhexidine wash daily	21 days	Marked improvement
6 years 10 months	RF D3 D4	Improvement, still inflammation	N	NA	Amoxicillin–clavulanic acid14 mg/kg PO q12h	Chlorhexidine wash daily	21 days	Mild improvement
6 years 11 months		Right lateral condylar fracture				Referral for treatment to orthopaedic specialistAmputation P3 RF D3 D4
7 years 8 months	?	?	N	NA	Amoxicillin–clavulanic acid14 mg/kg PO q12h	NA	42 days	Mild improvement
7 years 10 months	LF D3 D4	Inflamed, open wound	Y	?	Clindamycin 7 mg/kg PO q12h	NA	?	No
7 years 11 months	LF D3 D4	?	N	NA	NA	Amputation P3 LF D3 D4Histology performed	NA	Wounds healed well

LF = left forelimb; D = digit; LH = left hindlimb; ? = unknown; N = no; NA = not applicable; Y = yes; RF = right forelimb; P3 = third phalanx

Figure 5

Case 3: moderate paronychia of digit four of the right forelimb. Local inflammation and exudation are noted

Figure 6

Case 3: severe paronychia of digits 3 and 4 of the right forelimb. Marked ulceration and inflammation is present, exposing the bone of the third phalanx of digit 4

Figure 7

Case 3: distal phalanx (haematoxylin and eosin stain). The red dashed line outlines the entire profile of the distal phalanx, although the ungulate process (UP) was not sampled within the tissue section. The blue dashed lines outline the keratin claw (KC) and second phalanx (P2). Bone with cartilage of the retained primary spongiosa is particularly abundant in the extensor process (EP) and flexor tubercle (FT)

Figure 8

Case 3: distal phalanx (haematoxylin and eosin stain). The structure of osteopetrotic bone was characterised by cartilage (C) irregularly intermingled with bone (B). In this area of osteonecrosis, spaces that would normally contain fibrovascular tissue are occupied by necrotic debris (N) and inflammatory cell infiltrates (arrows)

Case 4

A neutered female 2-year-old DSH cat, located in the USA (number 210 in the database), was presented with a right patellar fracture. A chronic left patellar fracture and multiple persistent deciduous teeth were noted. At approximately 2 years of age, paronychia was first noted of digit one of the left forelimb and digits one and three of the right forelimb. For 14 months symptomatic treatment was trialled, involving a total of nine antibiotic courses. Culture and sensitivity were performed three times. A total of seven digits on only the forelimbs were affected. Radiographs were performed (Figure 9). The bones in both thoracic limbs showed a heterogeneous slight increase in bone density. For treatment details, see Figure 10 and Table 6. Owing to recurrent infection and discomfort, the third phalanx of all forelimb digits was amputated. During surgery, osteomyelitis was suspected owing to disintegration of the phalanges during the procedure. The amputated digits were placed in neutral buffered formalin and submitted for histopathological evaluation with routine processing and staining (haematoxylin and eosin). Each of the examined phalanges had abnormal organisation of bone that was characterised by hyaline cartilage intermingled with both mature lamellar bone and unmodelled amorphous bone (Figures 11 and 12). The overall density of bone was increased – no marrow tissue was present and intertrabecular vascular spaces were largely obliterated by cartilage or bone. At least two of the phalangeal bones had areas of suppurative inflammation, consistent with osteomyelitis (not shown). Five months after surgery the patient had recovered well and, as of the time of writing, the hindlimb nailbeds continue to show no sign of paronychia.

Figure 9

Case 4: radiographs performed as part of further investigations of paronychia. A heterogeneous slight increase in bone density was noted. An intravenous catheter was placed in the left cephalic vein. Marked soft tissue swelling was noted at digit one of the left forelimb and digit four of the right forelimb

Figure 10

Digits affected by paronychia in case 4, patient number 210. RF = right forelimb; LF = left forelimb; RH = right hindlimb; LH = left hindlimb; black = not affected; dark grey = amputated; white = amputated, not affected

Table 6

Detailed description of paronychia treatment of case 4, patient number 210

Age	Digits affected		Culture and sensitivity		Medical and/or surgical management			Improvement
	Location	Description	Performed	Growth	Antibiotics	Other treatment	Treatment length	Improvement
1 year 10 months	LF D1RF D1 D3	Overgrown nails; LF D1 discoloured growing into skin, with purulent debris expressed from nailbed; RF D3 growing into skin	N	NA	Cefovecin 8 mg/kg SC	Nail clip andchlorhexidine wash	Once	Resolved
2 years 4 months	LF D1 D2RF D1	Brown exudate-affected nailbeds	N	NA	Cefovecin 8 mg/kg SC	NA	Twice, 14 days apart	No improvement
2 years 5 months	LF D1 D2RF D1	Brown exudate-affected nailbeds	N	NA	Amoxicillin–clavulanic acid 13.75 mg/kg PO q12h	Chlorhexidine wash daily	28 days	Resolved
2 years 7 months	LF D1 D2RF D4 D5	Brown exudate-affected nailbeds	N	NA	Amoxicillin–clavulanic acid 13.75 mg/kg PO q12h	Chlorhexidine wash dailyLocal antibiotic ointment daily – nystatin–neomycin sulfate–thiostrepton–triamcinolone acetonide (Animax; Dechra)	28 days	No improvement
2 years 8 months	LF D1 D2 D5RF D4 D5	Brown exudate-affected nailbedsSmall open wound RF D4 with abscess formation	Y	Pasteurella multocida,Actinomyces species, Porphyromonas species,Bacteroides species	Cefovecin 8 mg/kg SCClindamycin 11 mg/kg PO q24h	Chlorhexidine wash daily	Two injections of cefovecin 14 days apart,6 weeks clindamycin	Moderate improvement – brown exudate remained present
2 years 10 months	LF D1 D2 D5RF D4 D5	Brown exudate affected nailbeds with mild purulent discharge	Y	Pasteurella multocida Clostridium species	Amoxicillin–clavulanic acid 13.75 mg/kg PO q12h	Chlorhexidine wash daily	28 days	Resolved
3 years 0 months	LF D1 D2 D5RF D1 D4 D5	Thickened and blunted claws, inflammation and brown exudate and mild purulent discharge from nailbeds	Y	Staphylococcus capitis	Cefovecin 8 mg/kg SCclindamycin 11 mg/kg PO q24h	Amputation P3 of all front limb digitsHistology performed	?	Wounds healed well

LF = left forelimb; D = digit; RF = right forelimb; N = no; NA = not applicable; SC = subcutaneous; Y = yes; ? = unknown

Figure 11

Case 4: distal phalanx (haematoxylin and eosin). A section from a relatively less affected digit has trabecular bone throughout most of the distal phalanx, although the extensor process (EP) has finely textured osteopetrotic bone with abundant cartilage. KC = keratin claw; P2 = second phalanx; UC = unguicular crest; FT = flexor tubercle

Figure 12

Case 4: distal phalanx (haematoxylin and eosin). Hyaline cartilage (C) is intermingled with bone (B), which includes both mature lamellar bone and unmodelled amorphous bone. The true density of bone is not apparent and clear space separating islands of cartilage and bone is an artefact of processing

Case 5

A 1-year-old neutered male DSH cat, located in the USA (number 215 in the database), presented for the extraction of deciduous teeth. Within a couple of months it sustained patellar fractures. At approximately 1.5 years of age paronychia was noted of the left hindlimb (digit unknown). For over 20 months the cat was medically managed with empirical and culture-based (performed once) antibiotics. A total of seven antibiotic courses were prescribed. Immunosuppressive medication was trialled. Treatments were sometimes successful; however, relapse of paronychia was common. All four limbs and a total of 14 digits were affected at some time period. For treatment details, see Figure 13 and Table 7. Owing to relapse and discomfort, amputation of P3 of all digits at 3 years of age was performed. At 10 years of age the cat sustained a right tibial fracture. At 11 years of age the cat was reported to be doing well and no further issues relating to the toes had occurred.

Figure 13

Digits affected by paronychia in case 5, patient number 215. RF = right forelimb; LF = left forelimb; RH = right hindlimb; LH = left hindlimb; black = not affected; dark grey = amputated; white = amputated, not affected

Table 7

Detailed description of paronychia treatment of case 5, patient number 215

Age	Digits affected		Culture and sensitivity		Medical and/or surgical management			Improvement
	Location	Description	Performed	Growth	Antibiotics	Other treatment	Treatment length	Improvement
1 year 5 months	LH D?	Nails missing	N	NA	NA	NA	NA	NA
1 year 8 months	LF D1 D2 D3RF D2 D3 D4 D5LH D2 D3 D4RH D1 D2	LF D1 D2 D3 ulcerated nailbedsRF D2 D3 D4 D5 nails missingLH D2 D3 D4 ulcerated nailbedsRH D1 D2 nails missing	N	NA	NA	Amputation P3 LF D1RF D?	NA	Wounds healed well
1 year 9 months	?	Nail missing, inflammation of nailbed	N	NA	Cefovecin 8 mg/kg SC	NA	14 days	Improvement
1 year 10 months	?	Two inflamed nailbeds	N	NA	Cefovecin 8 mg/kg SC	NA	14 days	Resolved
2 years 4 months	RH D4	Inflammation D4; however, all nails appeared thickened and irregular	N	NA	Cefovecin 8 mg/kg SC	NA	14 days	No
2 years 5 months	RF D2RH D4	Nailbed inflammation: all nails appeared thickened and irregular	N	NA	Marbofloxacin (dosage ?)	Prednisolone 1 mg/kg PO q12h 7 days; 1 mg/kg PO q24h 7 daysBarrier ointment (?)	14 days	Marked improvement
2 years 6 months	RH D4	Inflammation, much improvement	Y	Staphylococcus species	Amoxicillin–clavulanic acid12 mg/kg PO q12h	Prednisolone 5 mg PO q48h	14 days	Resolved
2 years 9 months	LF D4RF D4LH D4RH D4	Inflamed and mucopurulent discharge	N	NA	NA	Dexamethasone 0.1 mg/kg PO q48h	Ongoing	Mild improvement
3 years 1 month	LF D?	Multiple purulent nailbeds	N	NA	Cefovecin 8 mg/kg SC	NA	14 days	No
3 years 2 months	NA	NA	N	NA	Clindamycin (dosage ?)	Amputation P3 remainder of digits	?	All wounds healed well

LH = left hindlimb D = digit; ? = unknown; NA = not applicable; LF = left forelimb; RF = right forelimb; RH = right hindlimb; N = no; P3 = third phalanx; SC = subcutaneous; Y = yes

Discussion

Paronychia in cats with PADS has not previously been reported. Chronic paronychia is an additional clinical feature of PADS. Besides patellar fracture and deciduous teeth, mandibular and maxillary abnormalities and other fractures have been reported in cats suffering from PADS.^1–5 All cats included herein had patellar fractures and persistent deciduous teeth. Three of the five cats sustained other non-traumatic fractures in their life. All five cats had persistent nailbed inflammation, with recurrent infections. Antimicrobial therapy with or without non-steroidal anti-inflammatory drugs were trialled, which would often lead to temporary or no improvement of clinical signs. All cats had multiple digits of multiple limbs affected and eventually underwent amputation of the third phalanx of one or multiple digits.

Paronychia caused by bacterial infection can successfully be treated with antibiotics. If paronychia is unresponsive or relapses occur following a course of antibiotics, further investigations should be performed to identify the underlying disease, such as culture and sensitivity, dermatophyte culture, skin scrapes, cytological examination and/or nailbed biopsy.⁸ This was not always performed in the cases reported herein, and antibiotics were readily used without the benefit of culture and sensitivity results. Antibiotic prescribing was not always used according to the guidelines of the cascade and the authors strongly recommend the guidelines are followed to minimise the development of antibiotic resistance.

In challenging cases of paronychia or cats with severe discomfort, onychectomy can be performed as treatment and to assist in obtaining a definitive diagnosis.¹² Owing to the invasiveness of this procedure, it should only be considered for cats with recurrent and/or severe signs that do not resolve with medical management. In all the PADS cats reported herein, their signs could be considered recurrent, severe and non-responsive to medical management for the majority of the affected digits. A total of 36 digits were affected in this study, 17% (n = 6/36) resolved with medical management and 83% (n = 30/36) were treated successfully by amputation. Based on our study, we cannot conclude why paronychia sometimes resolved with medical management. It could be because of insufficient follow-up, or because of a different underlying pathology. Amputation should only be considered once medical management with investigations and proper use of antimicrobials, analgesia and topical treatment have failed.

Histopathological results were available for affected digits from two of the cats in this study (cases 3 and 4). These revealed abnormal bone of the distal phalanx with retention of cartilage. Both of these cats also had at least one digit in which neutrophilic inflammation involved digital bone, causing osteomyelitis with variable osteolysis and osteonecrosis, loss of the cornified claw sheath and/or ingrowth of nailbed epithelium. Based on these findings it could be speculated that persistent paronychia in cats with PADS involves break down of usual anatomical barriers to infection, particularly on the palmar/plantar aspect of the ungulate process of the distal phalanx. Underlying abnormal bone structure could render bone less likely to respond favourably to antimicrobial therapy, although a specific mechanism is not clear.

Research regarding the process and origin of PADS is ongoing. It is suspected that cats with PADS suffer from insufficiency fractures, where fractures occur when abnormally weakened bone is loaded normally. It has been postulated that these cats may have an underlying primary bone disorder. Primary bone modelling is suspected to be abnormal, and the abnormality is exacerbated in bones with a higher rate of remodelling. One of the affected cats had a generalised and marked increase in bone density on radiographs, throughout its skeleton, a phenomenon known as osteopetrosis.¹ The presence of cartilage within the distal phalanges of cats in this study also supports a form of osteopetrosis that is characterised by cartilage remnants of the primary spongiosa. Osteopetrosis has been well described in humans.¹⁴ It is a rare genetic disorder where patients have an increase in bone density due failure of bone resorption, specifically, a defect in osteoclast activity.^14–16 Patients suffer from persistent deciduous teeth, pathological fractures and osteomyelitis.^14,16 Depending on the form and severity of their disease, they are at increased risk for infections owing to, among other factors, impaired vascularity, anaemia and leukopenia.¹⁷ Osteopetrosis leads to poorly developed bone marrow causing anaemia, pancytopenia, osteomyelitis and sepsis.^4,14,18,19

Limitations of this case series are the small number of cases, the retrospective nature and variability of acquisition of information based on owner perception and clinical notes, particularly the specific digits involved.

Conclusions

Chronic paronychia is an additional clinical feature of PADS and the probable mechanism involves poor integrity of osteopetrotic bone, loss of normal nailbed anatomy and secondary osteomyelitis of the distal phalanx. A prospective study is warranted to document the frequency of paronychia in PADS and to investigate the pathogenesis further. In any cat with atraumatic patellar fractures and/or retained deciduous teeth, it is recommended to pay specific attention to the nailbeds. These lesions are commonly chronic in appearance and do not respond well to medical management. When medical management is instituted, antibiotics should be used according to the cascade and ideally following appropriate investigations to determine the cause. Amputation is not recommended as a first-line treatment and appropriate investigation and medical management of paronychia is recommended. Amputation should, however, be considered for cases where paronychia is unresponsive to medical management.

Footnotes

Accepted: 3 February 2021

Conflict of interest

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article’

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Ethical approval

This work involved the use of non-experimental animals only (including owned or unowned animals and data from prospective or retrospective studies). Established internationally recognised high standards (‘best practice’) of individual veterinary clinical patient care were followed. Ethical approval from a committee was therefore not specifically required for publication in JFMS.

Informed consent

Informed consent (either verbal or written) was obtained from the owner or legal custodian of all animal(s) described in this work (either experimental or non-experimental animals) for the procedure(s) undertaken (either prospective or retrospective studies). No animals or humans are identifiable within this publication, and therefore additional informed consent for publication was not required.

ORCID iD

Mariette A Pilot

Cynthia Bell

Hilary O’Dair

Sorrel J Langley-Hobbs

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