Palmar involvement in lichen planus
Department of Skin & STD, Kasturba Medical College, Manipal, Karnataka, India. firstname.lastname@example.org
Palmoplantar involvement in lichen planus is rare and often does not have the classically described clinical morphology, making it difficult to establish the diagnosis. We report a case in which asymptomatic solitary hyperpigmented patches with mild hyperkeratosis on the palms were the sole manifestation of lichen planus. Histopathology confirmed our diagnosis.
A 30-year-old male presented with asymptomatic palmar pigmentation of one-month duration. The lesions appeared spontaneously and were not associated with itching or pain. There was no history of similar or raised lesions on the body elsewhere and our patient denied a history of drug intake, promiscuity, or genital ulcers in the past. Cutaneous examination revealed solitary, well-circumscribed, brownish black patches with mild hyperkeratosis on both of the palms (Fig. 1), with sparing of the soles. The remainder of the physical examination was uneventful. We considered a differential diagnosis of tinea nigra, pigmented contact dermatitis, fixed drug eruption, and lichen planus. Repeated questioning failed to reveal any allergen that could be suspected of causing contact dermatitis. Our patient denied taking prior drugs or herbal medications. The potassium hydroxide (KOH) mount from the lesions was negative for fungal hyphae.
A biopsy for histopathology revealed markedly a hyperkeratotic and irregularly acanthotic epidermis with focal hypergranulosis and liquefactive degeneration of the basal layer. A band-like lymphocytic infiltrate was seen at the dermoepidermal junction along with pigment incontinence, consistent with our diagnosis of lichen planus (Figs. 2 & 3). The infiltrate was superficially placed and there were no eosinophils identified in the sections.
Palmoplantar involvement in lichen planus (LP) is rare and often does not have the classically described clinical morphology, making it difficult to establish the diagnosis . According to Sanchez et al., palmoplantar LP together with accompanying skin involvement accounted for 26 percent of cases; the lesions of LP were more frequently present on the soles than on the palms and the inner plantar arch was most commonly affected . Histopathology of palmoplantar lesions in LP has not been studied in detail. However, palmoplantar LP shows characteristic histopathology, very similar to that described in the literature for other sites .
In the English literature palmoplantar involvement in LP has been reported as hyperkeratotic scaly erythematous plaques (most common variant)  followed by a punctate keratosis-like pattern , diffuse palmoplantar keratoderma, and ulcerated lesions . Multiple variants may be present simultaneously in the same patient. Thappa et al. have reported diffuse pigmentation of the palms and soles along with lesions of LP elsewhere . In our case we could not find evidence of LP lesions on the body, apart from that described above.
In view of the pigmentation, tinea nigra, fixed drug eruption, and pigmented contact dermatitis, or dyshydrosis were considered in the differential diagnosis. These were appropriately ruled out on the basis of a negative KOH mount, the histopathology, and the absence of history of intake of medications.
To conclude, palmoplantar lesions in LP are uncommon and do not present with the classic violaceous, flat-topped, polygonal papules and Wickham striae that are typical of LP, making the clinical diagnosis challenging. Palmoplantar lichen planus is quite resistant to treatment. Topical and intralesional steroids, tacrolimus, tazarotene, cyclosporine, etretinate, and dapsone have all been tried with variable success . In our case we gave a trial with high potency corticosteroids to be applied twice daily and we will reassess at follow up.
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