Indolent systemic mastocytosis as the cause of a long history of unexplained hypotensive episodes

Assessment of patients with unexplained hypotensive episodes in outpatient practice is often challenging, with an extensive differential diagnosis. The prevalence of systemic mast cell disease (MCD) is unknown, and the diagnosis is often elusive because serum and urine markers may become positive only after one of the self-limited, recurrent hypotensive episodes. Nevertheless, MCD is increasingly recognized as a cause of unexplained hypotension, secondary osteoporosis, and anaphylactic reactions to Hymenoptera stings. We describe a 38-year-old man who had a 15-year history of undiagnosed, recurrent hypotensive episodes with stereotypic symptoms. Extensive evaluation during these years was unrevealing. On physical examination, he appeared to be a healthy man with a prominent macular rash. Results of skin biopsy showed tryptase-positive mast cells. He had markedly elevated serum tryptase levels, and results of bone marrow biopsy revealed 10% mast cells; all these findings were consistent with indolent systemic mastocytosis. Key features in his history and physical examination prompted the conclusive testing. The most telling features were hypotension, tachycardia, and the rash (urticaria pigmentosa).