Perforating lepromatous leprosy presenting as a generalised papulonecrotic eruption

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A 39-year-old man was referred to our institute with a diagnosis of perforating disorder. He presented with a six-month history of multiple asymptomatic skin-coloured raised lesions and atrophic scars all over the body. The lesions developed central ulceration and crusting and healed with atrophic scarring. He denied any hypopigmented patches, exposure to tuberculosis or leprosy. His family history was unremarkable. Cutaneous examination showed multiple discrete, skin-coloured papules measuring 0.5–1 cm, distributed on the trunk, both upper limbs and lower limbs. Several papules exhibited central ulceration and keratotic plugs. In addition, multiple annular, skin-coloured plaques of varying sizes (1 × 1 cm to 4 × 4 cm) were present on the trunk and extremities. Multiple atrophic scars of different sizes were also observed on the body [Figures 1a-c]. Examination of the peripheral nerves revealed symmetrical thickening of both ulnar and common peroneal nerves (grade 2) and reduced sensation on both legs. Histopathological examination of umblicated papules, showed an acanthotic epidermis, follicular plugging and macrophage granuloma, including foamy histiocytes [Figure 2a]. The granuloma was hugging and infiltrating the epidermis [Figures 2b and c]. Fite-Faraco stain demonstrated acid-fast bacilli (AFB) throughout the dermis and transepidermal elimination through the epidermis [Figures 3a and b]. AFB were noted in the keratinocytes and in the stratum corneum [Figures 3c and d]. Slit skin smear showed bacteriological index (BI) 6+ and morphological index (MI) 45%. A diagnosis of perforating lepromatous leprosy (LL) was made and he was started on multi-bacillary multidrug therapy.

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Figures 1 (a-c): Multiple, discrete, skin-coloured, umbilicated papules healing with atrophic scars noted over (a, b) trunk and (c) back.

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Figure 2a: Histopathology shows acanthotic epidermis, follicular plugging and macrophage granuloma, including foamy histiocytes (blue arrows) (Haematoxylin and eosin, 40x).

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Figure 2b: Multiple foamy histiocytes are noted in the dermis (blue arrows), impinging on the epidermis (Haematoxylin and eosin, 400x).

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Figure 2c: Macrophage granuloma invading the epidermis (blue arrow) (Haematoxylin & eosin, 100x).

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Figure 3a: Fite-Faraco stain demonstrates acid-fast bacilli within foamy histiocytes impinging on epidermis (red arrow) (400x).

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Figure 3b: Transepidermal elimination of acid-fast bacilli (red arrow), (400x).

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Figure 3c: Fite-Faraco stain showing acid-fast bacilli in epidermis, (red arrows) (100x).

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Figure 3d: Fite-Faraco stain showing acid-fast bacilli in the stratum corneum (red arrows) (400x).

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The diagnosis of generalised papulonecrotic eruption, presenting as papule-nodule which evolves to develop ulceration and atrophic scarring, is a clinical challenge. The various aetiologies for papulonecrotic lesions are papulonecrotic tuberculid (PNT), lymphomatoid papulosis and pityriasis lichenoides et varioliformis acuta (PLEVA). PNT manifests as crops of multiple, symmetrical, small, erythematous, inflammatory papules which undergo central ulceration and heal spontaneously within weeks, leaving varioliform scars, with a predilection for acral and extensor surfaces.¹ In India, one needs to rule out PNT before considering another disease due to the tuberculosis endemicity. PLEVA manifests as an abrupt eruption of erythematous macules that evolve into inflammatory papules with fine scale which undergo haemorrhagic necrosis and become ulcerated, leaving red-brown crusts that resolve with post-inflammatory hyper/hypopigmentation. Lymphomatoid papulosis, a nonaggressive T cell lymphoma, presents with recurrent red-brown papulonodular eruptions which become haemorrhagic and necrotic and spontaneously regress within 2 to 12 weeks with post-inflammatory pigmentation or characteristic atrophic scars. We did consider the above differentials before the skin biopsy; however, the thickening of the nerves compelled us to consider perforating leprosy as a differential.

Trans-epidermal elimination refers to the extrusion of dermal components through the epidermis or hair follicle. It is well-documented in entities like Kyrle disease, perforating folliculitis, reactive perforating collagenosis and acquired perforating dermatosis, all of which occur in a generalised distribution. However, elastosis perforans serpiginosa, perforating folliculitis and perforating granuloma annulare occur in localised distribution.² Trans-epidermal elimination of dermal components, including Mycobacterium leprae, is an unusual but significant phenomenon in leprosy, which plays a vital role in disease progression and transmission as well.³ The trans-epidermal elimination of M. leprae in histoid leprosy was previously reported, which presented as multiple papulo-nodules arising over normal skin with erosions and crusting.^4,5 A case of LL with trans-epidermal elimination, presenting as erosive lesions and atrophic scars predominantly on the extremities, has been previously reported.⁶ The spontaneous resolution of the perforated lesions may reflect two key mechanisms; transepidermal elimination could naturally expel bacilli-laden macrophages and necrotic debris, lowering the local antigenic load and aid in healing. Additionally, an Arthus (Type III) and delayed-type (Type IV) hypersensitivity response may lead to spontaneous healing, where complement-opsonised bacilli trigger macrophage activation and tissue reaction may lead to bacillary destruction and eventual scar formation.⁷ However, there is no previous report of generalised trans-epidermal elimination in LL mimicking papulonecrotic eruption.

We report this case to emphasise the rare generalised papulonecrotic morphology of perforating lepromatous leprosy resolving with atrophic scar which can be missed.