Unusual variations of gastrointestinal smooth muscle abnormalities associated with chronic intestinal pseudo-obstruction.

The clinicopathological spectrum of gastrointestinal (GI) smooth-muscle abnormalities associated with chronic intestinal pseudo-obstruction (CIPO) includes numerous heterogeneous conditions that are often ill-defined and poorly understood. Primary GI smooth-muscle abnormalities include familial and sporadic forms. Secondary involvement of GI smooth-muscle may result from associated GI and systemic conditions, but is less frequent than in adults. This study documents the clinicopathological findings observed in 12 South African patients with unusual forms of visceral smooth-muscle abnormalities not conforming to the diagnostic criteria of known primary visceral myopathies at the Tygerberg and Red Cross Childrens' Hospitals over a 14-year period (July 1985 through January 1999). Congenital muscle defects occurred in 5 patients where layers of bowel-wall muscle were absent or attenuated. Idiopathic fibrosis and ultrastructural features of perinuclear and mitochondrial vacuolisation were noted in 2 patients. A 21-year-old female with long-standing pseudo-obstruction demonstrated diminished immunohistochemical expression of enteric alpha-smooth-muscle actin without associated muscular degeneration or fibrosis. A secondary complication of dermatomyositis (bowel perforation) occurred twice in 1 patient. In 3 further patients (1 each with anorectal malformation, long-segment Hirschsprung's disease, and intestinal neuronal dysplasia), muscle fibrosis appeared during progression of the pre-existing disease. Visceral myopathies are poorly understood conditions that may present with CIPO. Unusual variations occur that do not conform to the usual recognised histological patterns. Secondary involvement may also be more common than anticipated in children. The challenge to further understanding these uncommon conditions lies in timely diagnosis and identification of early, subtle signs. Optimal and extensive application of various diagnostic modalities, including the development of new diagnostic tools, is of considerable importance in identifying hitherto unexplained CIPO due to GI smooth-muscle abnormalities.