Autoimmune enteric leiomyositis: a rare cause of chronic intestinal pseudo-obstruction with specific morphological features.

Autoimmune enteric leiomyositis is an extraordinary rare cause of acquired chronic intestinal pseudo-obstruction in children. We report a 5-year-old girl who developed chronic intestinal pseudo-obstruction 3 years after an autoimmune hepatitis. Mucosal biopsies of the upper gastrointestinal tract and colon showed minimal inflammatory changes. On full-thickness biopsies of the small intestine, a dense lymphocytic infiltrate of the muscularis propria was seen, mainly consisting of cytotoxic T lymphocytes. Smooth muscle fibers were degenerated and diminished, but the myenteric plexus was intact. The coexistence of an autoimmune hepatitis in our case indicates an expansion of autoreactive T cells to homologous self-antigens. It is of practical importance for histopathological diagnosis that inflammation in autoimmune enteric leiomyositis affects the muscularis propria of the small intestine, whereas mucosa and submucosa do not show severe inflammatory changes. Therefore, correct diagnosis may be missed in peroral and peranal mucosal biopsies, but full-thickness biopsies are required.