Pipestem capillaries in necrotizing myopathy revisited.

Pipestem-capillaries in necrotizing myopathy, have been reported as a feature of a distinct type of myopathy. Here, we analyze four muscle biopsy specimens from patients exhibiting endomysial fibrosis associated with pipestem capillaries using histological and electronmicroscopic techniques. However, only one case displayed all of the originally described features, including necrotic fibres, capillary thickening and lack of a significant lymphocytic inflammation, while one case exhibited striking capillary pathology with minimal necrosis and absence of inflammation, and the other two cases were accompanied by additional pathological features. These data support the existence of a microangiopathy with pipestem capillaries as a characteristic and distinct histopathological pattern, and indicate that it occurs in the context of a variety of muscular disorders broader than initially suspected. Furthermore, we show that the pipestem-capillary associated decrease in fibre size is at least in part a result of hypoxic changes.