A Case of Histoid Hansens Mimicking as Neurofibroma in Presentation in a Post Elimination Era

Introduction

Histoid leprosy (HL) is a well-known entity. In lepromatous leprosy patients, it is frequently present, either after dapsone monotherapy or rarely presents de novo. It is characterized by epidermal or subcutaneous nodules and plaques with distinct histopathology and peculiar bacterial morphology on apparently normal skin. Wade first proposed the word “Histoid Leprosy” as a histological notion of leproma with a strong bacillary content consisting of spindle formed cells, and a lack of globus development (so conspicuous in ordinary leproma). It has a chronically fibromatoid propensity.¹ It is observed in lepromatous patients that reappear in the context of dapsone resistance or rarely de novo after dapsone monotherapy and sometimes also in unstable borderline and interim leprosy. Resistance to dapsone, insufficient and irregular treatments, or the mutant bacterium Histoid bacillus may be responsible for the causes. Several studies with varied results have been reported.² We report a case of de novo histoid leprosy in a 25-year-old young man, who had numerous shiny nodules with abrupt eruptions associated with itching as major symptoms.

Case Report

A 25-year old male patient, baker by occupation complained of multiple nodules over the back, more over the lower back associated with itching of that area for six months. History of epistaxis, three to four episodes six months prior was given. There was no history of fever, pedal oedema, altered sensations or long-term drug intake for the same. Family history was non-contributory.

On clinical examination, multiple non-tender nodules, soft-to-firm in consistency, measuring 0.5 cm to 2 cm were noted. Papules were also present over the infra scapular region. (Fig.1) There was no impairment of pain, touch, temperature sensation. Mild bilateral ulnar nerve thickening was present.

A provisional diagnosis of suspicious case of de novo histoid leprosy was made keeping differential diagnosis as neurofibroma. Routine investigations, liver and renal functions were within normal limits, HBsAg was negative and HIV non-reactive. The Ziehl-Neelsen (ZN) stain showed numerous acid fast bacilli (AFB) with bacillary index 6+ (Fig. 2). Biopsy of lower back nodule was done and its histopathology report showed thinned out epidermis. Superficial and deep dermis showed dense aggregate of elongated foamy macrophages arranged in storiform pattern (Fig. 3).

A final diagnosis of de novo histoid leprosy was made. The case was informed and reported to District Leprosy Centre of the concerned area and was put on multi bacillary multi drug therapy (MB-MDT) and is presently on regular follow up.

Discussion

Prevalence of leprosy was estimated to be 0.62/10000 (National Leprosy Eradication programme; NLEP) in Kalaburagi in March 2017.³

The name “histoid” was provided as it was similar to a tumour that develops from histiocytic components that form spindles. It is quite similar to dermatofibroma and other histiocytic and fibrotic malignancies of the skin. The synonyms include histoid nodules and mycobacterium leprae histiocytoma (cutis and Leprous histiocytoma, Histoid Hansen’s). Some consider it a variation of leprosy and others a separate clinical entity. This is also found in borderline leprosy and intermediate leprosy patients.⁴

Its incidence was found to be between 2.79% and 3.60% among leprosy patients in India. In South India, it is not unusual. Male dominance exists, with the typical diagnostic age ranging from 21 years to 40 years.5 Singh et al, observed that 8.7% of lepromatous leprosy and 1.2% of all leprosy patients had an incidence of histoid leprae. Clinically, xanthoma, neurofibroma, dermatofibroma, reticulo-histiocytosis or cutaneous metastases are simulated with histoid leprosy. Each of them may be distinguished from histoid leprosy on the basis of its typical histopathology, lack of leprosy bacilli and the thickness of the nerves.⁵

It is usually observed in lepromatous patients who had recurrence following dapsone monotherapy, had dapsone resistance or had recurred at times in patients who experienced recurrence with supervised monthly MDT and in patients who were not treated. Ebenezer et al. documented a case of Histoid Hansen’s patient following seven years of MDT supervision.⁴

Multiple smooth, painless, firm, skin coloured to yellow brown nodules were observed on the skin. In seriously afflicted individuals, nodules may affect limbs, face, bony prominence and back, as well as mucosal membranes. Ears may not be impacted. Lesions of the histoid were also found in the peripheral nerve trunks and skin nerves.⁶ Epidermal atrophy due to the dermal development of the underlying leproma and a border area directly below an epidermis are classical histological findings. The leproma consists of a tangled or storiform pattern of fusiform histiocytes harbouring lepra bacilli. Histoid Hansen’s have three histological variations: Pure fuso-cellular, fuso-cellular with epithelioid component, and fuso-cellular with vacuolated cells. The third pattern is most frequently found.

In this case report, the histological investigation validated the clinical presentation of HL. In post leprosy elimination era, proper diagnosis and efficient treatment of HL is the need of the hour as it may trigger new cases and act as a reservoir.

Conclusion

The present case was recorded because of its unique clinical presentation and high bacillary burden in histoid leprosy, which can lead to an infection in the community, especially in this post-leprosy eradication age. Incomplete treatment might be due to poor-compliance (inappropriate counseling), limited access to medicinal products to be given at leprosy clinic. To prevent deformity and long-term handicap, it is necessary to trace the contact, in addition to pharmacotherapy of the condition.

Conflict of Interest

None.