Occult cutaneous mastocytosis

Mastocytosis is diagnosed without difficulty if it presents with easily rec ognizable lesions of urticaria pigmentosa. Recently, we have identified har dly visible skin lesions of mastocytosis in Hymenoptera venom allergic pati ents ("occult mastocytosis"). In addition, in approximately 15% of the pati ents with typical cutaneous lesions, urticaria pigmentosa was at first mist aken for other conditions and thus not linked to simultaneous symptoms of s ystem ic mastocytosis. In most patients with unrecognized mastocytosis,the diagnosis was supported by raised basal serum tryptase levels. Cutaneous ma stocytosis is often overlooked and more frequent than assumed. Measurement of basal serum tryptase concentrations can make an important contribution t o the diagnosis of mastocytosis, but it does not replace a meticulous skin examination.