Progressive systemic sclerosis of the gastrointestinal tract and hereditary hollow visceral myopathy: two distinguishable disorders of intestinal smooth muscle.

The purpose of this study was to determine whether progressive systemic sclerosis (PSS) of the gastrointestinal tract and hereditary hollow visceral myopathy are two distinguishable disorders of intestinal smooth muscle. We coded and blindly reviewed 50 specimens of tissue from the small intestine of 15 normal controls, 4 patients with visceral myopathy, 5 patients with PSS and intestinal pseudoobstruction, and 5 patients with PSS but no pseudoobstruction. We determined that there is a fundamental difference between the pathology of these two disorders. In visceral myopathy, the smooth muscle is characterized by vacuolar degeneration and fibrosis. In PSS, smooth muscle fibrosis is present but vacuolar degeneration is absent. Although smooth muscle cells are decreased in number in both disorders, those that are present in PSS are morphologically normal by light microscopy, whereas most of those present in visceral myopathy are degenerated. Visceral myopathy and gastrointestinal PSS are two distinct disorders of smooth muscle which are easily distinguished by conventional light microscopy. Their dissimilar appearances and the familial nature of visceral myopathy suggest that they result from quite different causes.