Zosteriform multidermatomal nodules and plaques in a case of lepromatous leprosy: an uncommon presentation

Introduction

Leprosy caused by Mycobacterium leprae is characterised by wide variations in the clinical manifestations ranging from involvement of a single nerve to countless nodules and damage to the internal organs 1. Differing presentations, in turn, is a reflection of an infected individual's immune status. Varied manifestations of LL have been reported (Table 1); 2-6 however, a multi- dermatomal pattern of nodules is hitherto unreported, and we suggest a hypothesis for its presentation.

Case report

A 55-year-old man presented with skin-coloured raised lesions over the left trunk and left thigh for the previous one year with a history of loss of sensation over these lesions. On examination, some nodules were coalescing to form plaques, predominantly distributed over the left lower back and posterior left thigh in a dermatomal pattern corresponding to T8-L1 and L5-S2, respectively (Figure 1a, 1b, 1c). Multiple small papules and nodules were also present over the left eyelid, upper lip and left neck and trunk on top of normal-looking skin. The nodules were soft to firm, non-tender and had a smooth and shiny surface. Bilaterally enlarged and firm ulnar, lateral popliteal and radial cutaneous nerves were palpable. Loss of sensation to temperature and fine touch was found over the plaques with intact sensation over the rest of the body. Motor examination and general and systemic examination were normal. OPEN IN VIEWER

Slit skin smear (SSS) tests from ear lobes and the plaque showed numerous acid-fast bacilli (BI- 6+/globi).

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Table 1.

A typical cutaneous presentations of lepromatous leprosy.

Erythema gyratum repens-like pattern 2

Verrucous lesion of lepromatous leprosy 3

Erythema multiforme-like lesion 4

Single plaque on the leg 4

Lymphadenopathy masquerading lymphoma 4

Single nodule on the face 4

Zosteriform, segmental, dermatomal4,5

Longstanding leg ulcer4,6

Spontaneous skin ulceration 6

Histoid leprosy 6

Lucio leprosy 6

He had been on irregular leprosy treatment. Bacilli were found, however, to be sensitive to rifampicin, dapsone and ofloxacin. Skin biopsy revealed thinning of the epidermis, subepidermal grenz zone and pan-dermal infiltration by sheets of foamy macrophages with the fite stain revealing globi of lepra bacilli (Figures 2a, 2b). A final diagnosis of LL was confirmed and treatment was initiated with World Health Organization-recommended multidrug therapy (WHO-MDT) for 12 months. OPEN IN VIEWER

Discussion

Leprosy presents with a broad clinical and histopathological spectrum that is better correlated with the immunological response of the patient than with the initial bacillary invasion which is classically neurotropic. It has also been established that in anergic leprosy, a bilaterally symmetrical, distribution of hypopigmented macules, nodules or plaques are seen; ¹ and while many unusual and protean manifestation of LL have been described,^2–5 a dermatomal presentation is decidedly uncommon.^4,5

It has been postulated that this was consequential to the selective multiplication of M. leprae in the nerves of select dermatomes. ⁷ The sensory fibres of the skin are the first to be affected, and bacilli can be traced in diminishing numbers up the nerve trunks as far as the sensory dorsal root ganglion, but despite extensive search they are not found higher up the cord or in the brain. ⁸ Motor nerves are affected later. The anergic state of LL coupled with irregular therapy in our case may have led to the invasion of micro-organisms beyond the perineurium into the dermis, thus accounting for the dermatomal distribution. The previous two cases reported were notably also of the multibacillary spectrum.^4,5 While LL is characterised by anergy and lesions are usually bilateral, a unilateral distribution led us initially to believe that the lesions were of a histoid pattern. A possible explanation is an initial borderline leprosy that had downgraded; however, biopsy findings were not supportive of this supposition. Irregular treatment may explain the histoid morphology, but the possibility of resistance had been ruled out by appropriate testing.

Cutaneous diseases known to follow a nodular dermatomal distribution include neurofibromatosis, spiradenomas, leiomyomas, trichoepitheliomas and vascular hamartomas. Leprosy may be added to this list, with other infectious granulomatous disorders, such as syphilis and cutaneous leishmaniasis, and our multidermatomal presentation adds to the uncommon protean manifestations of leprosy. ⁶