Histoid leprosy in Singapore.

Histoid leprosy is a rare variant of lepromatous leprosy. This is the first documented case of histoid leprosy in Singapore. The patient was diagnosed as borderline leprosy in 1973, remained untreated and progressed to lepromatous leprosy. The characteristic histoid lesions were firm pruriginous nodules on the dorsum of his feet. The histology showed a pseudocapsulated tumour with fibroblasts and histiocytes filled with lepra bacilli. Electron microscopy showed fibroblasts, macrophages with bacilli and plasmacytoid cells with active endoplasmic reticulum. He was found to be dapsone-resistant and the lesions cleared with clorphazimine. Immunological defects were not detected.