Ultrastructural demonstration of abnormal multiaxonal Schwann-cell units in Hirschsprung's disease

The pathophysiology of Hirschsprung's disease is not fully understood. Using light microscopy we have previously demonstrated the absence of a unique Schwann-cell antigen in the circular muscle of aganglionic colon identified by D₇ monoclonal antibody. In an attempt to characterise the morphological changes in neuronal cells at subcellular level, we studied innervation patterns in normal and aganglionic colon by electron microscopy. The most striking observation on ultrastructural serial examination of the entire resected specimen of colon from patients with Hirschsprung's disease was the presence of grossly swollen monoaxonal or oligoaxonal Schwann cell units with loss of cellular contents in the circular muscle of aganglionic colon. The extent of subcellular changes in Schwann cells and axons corresponded with a diminution of immunoreactivity with a panel of neuronal cell antibodies. These ultrastructural findings suggest that degenerative changes in Schwann cells and axons within the circular muscle coat of aganglionic segment may be a significant factor in the pathogenesis of Hirschsprung's disease. Offprint requests to: P. Puri