Systemic, cerebral, and pulmonary segmental mediolytc arteriopathy: Villainous masqueraders of vasculitis.

Segmental mediolytic arteriopathy (SMA) is a newly described and uncommon variant of arterial fibromuscular dysplasia that affects principally visceral small and medium sized arteries. SMA is characterized by myolytic dysplasia of the arterial media, intramural dissection, and thrombosis or ruptured aneurysms resulting in visceral hemorrhage and infarction as the dire consequences. Because of its relative obscurity and frequent angiographic manifestation of microaneurysms, clinically SMA mimics polyarteritis nodosa, and the patient so diagnosed had been treated with immunosuppressive therapy with a catastrophic outcome. Five new cases of unsuspected SMA are described herein, three involving visceral arteries and, for the first time, one case each affecting the cerebral and pulmonary parenchymal arteries. Three of the five patients did not survive because SMA remained unrecognized until after death and a subsequent review of the biopsy and autopsy specimens. Death in each of the three patients was directly attributable to complications of SMA or indirectly to septic complications of the immunosuppressive therapy for the misdiagnosed vasculitis. Clinicians and pathologists alike should become better acquainted with this unusual form of noninflammatory arteriopathy, so as not to misdiagnose it as vasculitis.