Question:

A 63-year old farmer complained of persistent ugly and itchy rash at legs for the past ten years. He had tried various topical therapies to the lesions with minimal improvement. On examination, there were multiple tiny brownish hyperkeratotic papular eruptions at the anterior shin of both legs. It was rough and firm on palpation and resembled the surface of the litchi (荔枝) skin. There were no other abnormalities including the mucous membrane. He enjoyed good health all along and had no major illness.

This patient is suffering from cutaneous lichen amyloidosus. Lichen amyloidosus is the commonest form of localized cutaneous amyloidosis in Chinese patients. It usually presents as a persistent, pruritic papular eruption on the shins as shown in this case. The extensor of thighs, forearms and upper arms may also be involved. It consists of multiple discrete papules, which are scaly, pigmented and closely simulate hypertrophic lichen planus or lichen simplex chronicus. The resemblance of litchi (荔枝) skin is characteristic. Lichen amyloidosus may persist for many decades with localized itchiness and is particularly common in the Chinese population. Treatment is symptomatic and the response to treatment is seldom satisfactory. The most potent topical steroid can be tried with or without occlusion. It helps in the short term. Surgical removal by dermabrasion and carbon dioxide lasers have been tried with various rates of success but they may not be feasible for multiple extensive lesions. However, this condition is a benign cutaneous condition and should not be confused with the much rarer form of cutaneous lesions of primary or myeloma-associated systemic amyloidosis. Systemic amyloidosis usually presents as triad of carpal tunnel syndrome, macroglossa and some waxy, translucent or purpuric papules.

Lesions of hypertrophic lichen planus often occur on the lower limbs but they usually present as confluent plaques with a violaceous and erythematous background. Lichen simplex chronicus is a form of chronic eczema with thickened plaque of excoriated eczematoid rash. Lichen simplex chronicus is commonly found on nape of neck, scalp, leg and ankles.