Progressive mucinous histiocytosis is a very rare, benign, non-Langerhans' cell histiocytosis limited to the skin. In total ten patients (all women) in four families and three sporadic cases have been reported. We report here the first published case of a male patient with progressive mucinous histiocytosis. The multiple red papules on the scalp and forearms were asymptomatic and had slowly increased over approximately the past 20 years. The patient's mother had similar lesions. Histological examination revealed nodules in the dermis with histiocytes and mucin deposition. The histiocytes stained positively with CD31 and negative with CD34, CAM 5.2, PGM-1 and factor XIIIa. Ultrastructurally, the histiocytes showed numerous circular myelin bodies and zebra bodies reminiscent of those seen in lysosomal storage diseases. The genetic transmission of hereditary progressive mucinous histiocytosis remains unclear; we assume an autosomal dominant transmission with some hormonal factor that makes hereditary progressive mucinous histiocytosis more likely in women.