Structural immaturity of the pylorus muscle in infantile hypertrophic pyloric stenosis

Recent reports indicate that extracellular matrix and cytoskeleton plasmale mmal elements are altered in infantile hypertrophic pyloric stenosis (IHPS) . Desmin is a cytoskeletal protein that is important for the organization a nd function of muscular fibers. It has been found to be increased in the sm ooth muscle in chronic intestinal pseudo-obstruction and in skeletal muscle in some forms of myopathies as well as in unexplained hypertrophic cardiom yopathies. The aim of this study was to analyze the expression of desmin in IHPS. Full-thickness muscle-biopsy specimens were obtained from 8 IHPS pat ients (age range 23 to 41 days) at pyloromyotomy, from 8 age-matched contro ls 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-biot in-peroxidase complex method with anti-desmin and visualized by development with 3-diaminobenzidine tetrahydrochloride. Pyloric muscle in IHPS demonst rated strong desmin immunoreactivity. The expression of desmin was also str ong in the muscular layers of fetal pylorus. In the age-matched controls ab sent 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, thu s causing motility dysfunction. The similar pattern of desmin expression in IHPS and fetal pylorus suggests that the organization of intermediate fila ments in IHPS is in a fetal stage of development.