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A 76-year-old man with a 52-year history of urticaria pigmentosa was found to have an elevated serum tryptase level as well as osteoporosis. Histopathologic alterations of one his skin lesions showed an infiltrate of mast cells. Urticaria pigmentosa patients are at risk for osteoporosis because of elevated heparin and stem-cell factor levels. These patients should be screened with serum tryptase levels and bone density studies to detect osteoporosis, regardless of their age.

Out of 21 male patients with osteoporosis who visited an outpatient clinic for endocrine diseases in two years (1994-1995), three had systemic mastocytosis as diagnosed histopathologically. Two of these had characteristic features of urticaria pigmentosa, consisting of multiple brown nodules on the skin of trunk and extremities, and a positive Darier sign. In all of them the excretion of the histamine metabolites methylhistamine and methylimidazoleacetic acid in a 24-hour urine specimen was increased. When osteoporosis is diagnosed in men or premenopausal women, underlying pathology could be considered. Cautious investigation of signs and symptoms of systemic mastocytosis in such patients might prove this disease be less rare than is often assumed.

A case of systemic mastocytosis in a 33-year-old man, with multiple spine fractures caused by severe osteoporosis, is presented. The diagnosis could only be established three years after the initial symptoms, when the patient developed skin eruption. Skin and bone biopsy, as well as histamine dosage, confirmed the diagnosis.