Solitary plaque of borderline lepromatous leprosy clinically masquerading as paucibacillary leprosy

Case report

A 28-year old man presented with a single asymptomatic, well-defined, erythematous infiltrated plaque with sloping margins, measuring 10  ×  8 cm, extending horizontally from the right temporal area to the medial canthus of the left eye and vertically from the forehead to the dorsum of the nose sparing the ala and nasal tip, for two months (Figure 1A-B). There was no history suggestive of systemic complications. On examination, the lesion was dry and scaly with hair loss. Its overlying temperature was raised, tenderness was present and there was loss of sensation to cold and hot temperature, though pain and touch sensations were intact. There were no other skin lesions. The right great auricular nerve was nodular and non-tender. Ocular examination revealed a reduced aperture of the right eye with mild watering, conjunctival congestion and oedema of the right upper eyelid. Slit lamp examination and fundoscopy were unremarkable. No sign of facial or trigeminal nerve palsy was present. Sensory and motor examination were normal.

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Figure 1.

1A Well-defined erythematous infiltrated plaque with sloping margins and fine white loose scaling, measuring 10  ×  8 cm, extending horizontally from the right temporal area to the medial canthus of the left eye and vertically from the forehead to the dorsum of the nose. 1B Right side of the face showing plaque covering the forehead, dorsum of nose, upper eyelid, zygomatic area and ear.

Clinically a possibility of borderline tuberculoid (BT) leprosy with Type 1 reaction (T1R) was considered. Slit skin smear (SSS) from the lesion revealed a bacillary index (BI) of 2  +  with solid staining bacilli. Histopathological examination revealed atrophy of the epidermis and a grenz zone. Dermis and subcutaneous fat showed discrete to confluent granulomas with numerous neutrophils and few foamy histiocytes in perivascular, perineural and peri-adnexal distribution (Figures 2A-C). Fite stain revealed solid staining bacilli with BI of granuloma as 2 + (Figure 2D). Based on SSS examination and histopathologic findings, a final diagnosis of borderline lepromatous (BL) leprosy with Type 2 reaction (T2R) was made. Our patient was started on WHO multibacillary multidrug therapy (MB-MDT) and oral prednisolone 40 mg daily. Oral prednisolone was gradually tapered and stopped in 12 weeks, while MB-MDT was administered for one year.

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Figure 2.

2A, 2B Discrete to confluent granulomas comprising of abundant neutrophils and few foamy histiocytes in perineural and perivascular dermal locations (haematoxylin and eosin, × 400). 2C Subcutis showing aggregates of foamy histiocytes and neutrophils in perivascular distribution (haematoxylin and eosin, × 400). 2D Solid staining acid fast bacilli seen (Fite stain, × 1000).

Discussion

WHO has classified leprosy as paucibacillary (PB) and multibacillary (MB). PB leprosy is defined as a case with 1–5 skin lesions in the absence of bacilli on SSS, and MB leprosy as a case with either >5 lesions; or with nerve involvement or with presence of bacilli on SSS.

Localised forms of MB leprosy have been uncommonly reported in literature.^1–4 The localization of lesions in leprosy is due to Mycobacterium leprae invasion following trauma, tattooing or thorn pricks. However, a single lesion in a BL leprosy patient with T2R has not been described. Though typically T2R presents as painful erythematous nodules, less common morphologic variants are vesicobullous, pustular, ulcerative, necrotizing, erythema multiforme-like and Sweet syndrome-like. Once case has been reported of BT downgrading to BL, clinically presenting as T1R. This was, however, histologically confirmed as erythema nodosum. ⁵

The clinical presentation in our patient was compatible with BT leprosy with T1R, however SSS from the lesion and histopathology were suggestive of BL leprosy with T2R. Interestingly, the patient did not develop typical lesions of ENL or any constitutional symptoms. Correlation between clinical and histopathological diagnosis is shown to be maximum in lepromatous leprosy (LL) (97.1%), followed by BL (95.1%) and BT (86.5%). ⁶ Immunologically unstable nature of borderline disease could explain their lower rates of clinicopathological correlation.

Conclusion

The present case of solitary plaque in BL leprosy with T2R exemplifies the importance of performing SSS and histopathological examination in every case of leprosy so as to classify patients correctly along the disease spectrum. Correlation of clinical diagnosis with bacteriological and histological findings is imperative for accurate classification and appropriate treatment as undertreatment of MB case can lead to complications and secondary drug resistance. Proper treatment is also required to prevent community transmission.