Loss of interstitial cells and a fibromuscular layer on the luminal side of the colonic circular muscle presenting as megacolon in an adult patient

Background-Animal studies have shown that the neuromuscular structures on t he luminal side of the colonic circular muscle coordinate circular muscle a ctivity. These structures have been identified by electron microscopy in th e normal human colon, but have never been thoroughly studied in patients wi th acquired intestinal hypoganglionosis. Aims-To perform histological, immunocytochemical, and electron microscopic examinations of the colon of a patient with acquired intestinal hypoganglio nosis presenting as megacolon. Patient-A 32 year old man with a one year history of constipation and abdom inal distention, a massively dilated ascending and transverse colon, and a normal calibre rectum and descending and sigmoid colon. He had a high titre of circulating serum anti-neuronal nuclear antibodies. Methods-Histology, immunocytochemistry (for neurofilaments, neurone specifi c enolase, synaptophysin, glial fibrillar acidic protein, S100 protein, and smooth muscle alpha-actin), and electron microscopic examinations on the r esected colon. Results-The number of ganglion cells and nerve trunks was decreased through out the colon. Disruption of the neural network and a loss of interstitial cells of Cajal were observed on the luminal side of the circular muscle; in their price, the non-dilated colon contained a hypertrophic fibromuscular layer. Conclusions-Striking architectural alterations occurred at the site regarde d as the source of the coordination of colonic circular muscle activity in an adult patient with acquired intestinal hypoganglionosis presenting as me gacolon.