Question:

A 40- year old man presented with multiple annular itchy macules and plaques over his flanks, inner thighs and forearms for about half a year. The rash was progressively enlarging with minimal superficial scaling. He had tried some topical antifungal agent without response. On physical examination, apart from the annular rash, there was no lymph node palpable.

Answer: B. Mycosis fungoides

Mycosis fungoides usually presents as annular plaques that simulate tinea infection. However, it does not respond to antifungal agent and it presents in a more bizarre pattern. Microscopic examination shows skin with mild epidermal thickening, prominent epidermotropism, small Pautrier's collections and a linear array of convoluted lymphocytes along the dermal epidermal junction. The papillary dermis shows fibrosis. There is a band-like infiltrate of lymphocytes in the upper dermis. Immunohistochemical studies show that the lymphocytes are CD3 positive and CD20 negative, indicative of T- cell lineage. In late stage, tumour may arise from the plaques and lymphadenopathy may be detected. The treatment aim is to relieve the symptom of itch by potent topical steroid in the initial stage (patch stage). If a large area of the body is involved by plaques, photochemotherapy and total body irradiation are the treatment of choice. For tumour stage, chemotherapy may be needed but the response is usually poor.