Deficient alpha-smooth muscle actin as a cause of functional intestinal obstruction in childhood.

PURPOSE: Most functional intestinal obstruction in childhood is due to defects in the enteric innervation. Functional intestinal obstruction due to smooth muscle disorders is rare. The aim of this study was to describe four patients with functional intestinal obstruction where the only histopathological abnormality was deficient, alpha-smooth muscle actin (alpha-SMA) in the circular muscle of their small bowel.

MATERIALS AND

METHODS

Resected intestinal segments from four children with functional intestinal obstruction were either snap frozen or embedded in paraffin wax, and transversely sectioned. Sections were examined by routine H&E staining, AChE and NADPH-diaphorase histochemistry, and immunohistochemistry using PGP9.5 and alpha-SMA antibodies. Normal age-matched tissue was used as controls.

RESULTS

All four patients demonstrated normal innervation in the small and large bowel. We observed striking differences in the expression of alpha-SMA within the intestinal muscle layers in all four patients. There was a markedly decreased level of alpha-SMA in the smooth muscle compared to the longitudinal muscle in the small bowel in each patient. All other regions of the intestine examined showed normal levels of alpha-SMA, with similar levels expressed in both the circular and longitudinal muscles.

CONCLUSION

The decreased level of alpha-SMA in the smooth muscle of these patients causes a serious mechanical defect, thus interfering with normal intestine motility. These findings suggest that patients with functional intestinal obstruction should have a comprehensive investigation of the intestinal smooth muscle in addition to the assessment of the enteric nervous system.