Anal skin tag – An unusual presenting feature of food protein-induced allergic proctocolitis in a neonate

1 Introduction

Food protein-induced allergic proctocolitis (FPIAP) is a common cause of rectal bleeding in breastfed or formula-fed babies in the first year of life. The presenting symptoms of FPIAP are blood in stools, colic, increased gas and rarely constipation [1, 2]. Anal skin tag (AST) is a benign growth of excess skin around the anus and is commonly seen in anal fissures, constipation, Crohn’s disease (CD) and ulcerative colitis [3, 4]. To date AST has rarely been described with FPIAP in literature. We herein report a rare case of a neonate with FPIAP who presented with blood in stools and AST and was managed successfully.

2 Case report

Our patient is a term male born by normal vaginal delivery to non-consanguinous parents. He presented to our neonatologist on day twenty six of life with history of passing blood intermittently in stools for two days. The stools were well-formed with soft consistency. The baby passed stools two to three times a day. He was subsequently referred to pediatric gastroenterologist for further evaluation. There was no fever, vomiting, or lethargy. The baby had some discomfort during defecation, however the stool consistency was soft. He was exclusively breast-fed, well-appearing with no failure to thrive. Two anal skin tags were present but there was no evidence of anal fissures or haemorrhoids (Fig. 1). Anal tags were not present at birth as confirmed by the medical records and the history given by parents. Rest of the examination findings were unremarkable. The differential diagnosis considered were infectious colitis, idiopathic neonatal transient colitis, FPIAP, late-onset haemorrhagic disease of newborn, volvulus, and very early-onset inflammatory bowel disease (VEO-IBD). Empirical oral antibiotic for infectious colitis was started awaiting culture reports. Investigations done showed mild anaemia and hypoalbuminemia. There was no eosinophilia in the blood counts. IgE levels could not be done due to financial constraints. Stool microscopy showed 20 pus cells/hpf and stool calprotectin was 221 mg/Kg (N < 40). Ultrasound of abdomen was normal. Coagulation profile, blood culture and stool culture were normal. Mother was advised to eliminate cow’s milk protein (CMP), soy, eggs and nuts from her diet. Transient improvement for one week after completion of antibiotics was seen followed by recurrence of blood in stools. Breastfeeding was stopped and a trial of extensive hydrolysed milk was given without any benefit.

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Fig. 1

Anal skin tag.

In view of increasing size of AST, persistent blood in stools and poor response to maternal diet restriction and extensively hydrolysed formula (eHF); endoscopy was planned to rule out VEO-IBD. Upper gastrointestinal endoscopy was normal. Colonoscopy showed mucosal oedema, lymphoid nodular hyperplasia, patchy erythema and focal active colitis in rectum and sigmoid colon suggestive of FPIAP (Fig. 2). The biopsy of AST showed fibroepithelial polyp. In view of poor response to eHF, the baby was started on amino acid based formula (AAF) with complete recovery over two weeks. Repeat stool examination and stool calprotectin were normal. Re-introduction of breastfeeding was tried at another hospital resulting in recurrence of blood in stools. Breastfeeding was stopped and the baby was continued on AAF. On follow up after two months the baby was thriving well and asymptomatic. Conservative management was planned for AST and its size progressively decreased after introduction of AAF.

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Fig. 2

Colonoscopy showed mucosal oedema, lymphoid nodular hyperplasia, patchy erythema and focal active colitis in rectum and sigmoid colon suggestive of food protein-induced allergic proctocolitis.

The biopsy of AST in our case showed fibroepithelial polyp without granuloma. Fibroepithelial anal polyp or AST are commonly found at the dentate line, anal mucosa or in the perianal skin [3, 5]. They originate from anal papillae and become enlarged in response to chronic irritation, inflammation, injury or infection. They are usually associated with conditions such as fissure, constipation, haemorrhoids or IBD. Granulomas are found in 30% of AST in cases of Crohn disease [6]. In presence of AST, Bonheur et al. have suggested to consider the diagnosis of CD in proper clinical context even before any invasive investigation is pursued [4]. According to Papadopoulos et al. fibroepithelial anal polyp is a rare physical sign and indicates chronic anal pathology [5]. Histologically, fibroepithelial polyp consists of a fibrous stroma covered by squamous epithelium [3, 4]. Common conditions presenting with blood in stool and AST in infants include anal fissure, haemorrhoids, constipation and VEO-IBD [4–6]. The association of anal skin tag with FPIAP observed in our case is unusual and has rarely been reported in literature. However to establish independent association of anal skin tag with FPIAP, further studies with greater sample size are required. Non-inflamed AST are painless, rarely require treatment, and should not be excised [4, 5].

FPIAP is a benign transient condition and represents the milder end of the non-IgE-mediated food hypersensitivity spectrum [1, 2]. Its prevalence is around 1.5% and approximately 60% of the cases are observed in exclusively breastfed babies. It is usually caused by cow’s milk protein, soy, egg, nuts, and corn proteins [1, 7]. FPIAP presents within the first six months of life with normal to moderately loose stools and intermittent blood streaks. Other symptoms include colic, reflux, eczema, increased gas, pain with defecation, intermittent emesis and rarely constipation. There is no failure to thrive and most cases have a positive family history of atopy [1, 7]. FPIAP is almost always a clinical diagnosis with exclusion of other causes of rectal bleeding. The diagnosis is confirmed after resolution of symptoms upon elimination diet, in the mother or the baby. Patients with atypical features at presentation, or those who do not respond to a careful and consistent elimination of the suspected food, should undergo a more extensive evaluation [1, 7]. This may include food challenge, flexible sigmoidoscopy or colonoscopy, allergy testing or other tests as guided by the infant’s symptoms. The presence of AST, persistent blood in stools and poor response to eHF were the atypical features in our case and hence endoscopy was performed. FPIAP predominantly affects the rectosigmoid. Colonoscopy demonstrates mucosal oedema, lymphoid nodular hyperplasia, patchy erythema and eosinophils in the lamina propria and muscularis mucosa [1, 7]. Majority of breastfed infants with FPIAP respond to elimination of CMP, and in resistant cases soy, egg and nuts, from the mother’s diet [1, 8]. Breastfeeding should not be discontinued if the mother is compliant with her diet restriction. For formula-fed infants, cow’s milk or soy-based formulas should be replaced with an eHF, and in resistant cases (about 5%) with AAF [1, 8]. FPIAP has an excellent prognosis with majority of infants being able to tolerate cow’s milk and soy products by one year of age. Di Nardo G et al. found that presence of severe FPIAP is a risk factor for development of functional gastrointestinal disorder in later childhood [9]. However, progression to persistent food allergy or chronic colitis including inflammatory bowel disease is extremely rare [1, 10].

4 Conclusion

Rectal bleeding in infants can cause serious concern and parental anxiety leading to urgent investigation and hospital care. Through this case, we wish to highlight that clinicians should include FPIAP, a benign self-limiting condition, in their differential diagnosis in a well-appearing infant with blood in stools and anal skin tag. Failure to appreciate this entity may lead to inappropriate invasive diagnostic or therapeutic intervention.