Structural immaturity of the pylorus muscle in infantile hypertrophic pyloric stenosis

Recent reports indicate that extracellular matrix and cytoskeleton plasmalemmal elements are altered in infantile hypertrophic pyloric stenosis (IHPS). Desmin is a cytoskeletal protein that is important for the organization and function of muscular fibers. It has been found to be increased in the smooth muscle in chronic intestinal pseudo-obstruction and in skeletal muscle in some forms of myopathies as well as in unexplained hypertrophic cardiomyopathies. The aim of this study was to analyze the expression of desmin in IHPS. Full-thickness muscle-biopsy specimens were obtained from 8 IHPS patients (age range 23 to 41 days) at pyloromyotomy, from 8 age-matched controls without evidence of gastrointestinal (GI) disease at autopsy, and from 2 stillborns who died at 27 and 30 weeks of gestation without evidence of GI disease. Indirect immunohistochemistry was performed using the avidin-biotin-peroxidase complex method with anti-desmin and visualized by development with 3-diaminobenzidine tetrahydrochloride. Pyloric muscle in IHPS demonstrated strong desmin immunoreactivity. The expression of desmin was also strong in the muscular layers of fetal pylorus. In the age-matched controls absent or weak desmin immunoreactivity was seen in the pyloric muscle layer. The increased amount of desmin in hypertrophied pyloric muscle in IHPS may result in inco-ordination of contraction and relaxation of the pylorus, thus causing motility dysfunction. The similar pattern of desmin expression in IHPS and fetal pylorus suggests that the organization of intermediate filaments in IHPS is in a fetal stage of development.