Acquired myopathic intestinal pseudo-obstruction may be due to autoimmune enteric leiomyositis

We describe a previously healthy boy who developed intestinal pseudo-obstruction following an episode of gastroenteritis at age 2 years. At presentation, the patient had mildly raised erythrocyte sedimentation rate and C-reactive protein level, and elevated antineutrophil cytoplasmic antibodies, antinuclear anti-DNA, and anti-smooth muscle antibodies. His electrogastrography was myopathic with no dominant frequency. First full-thickness intestinal biopsies showed a T lymphocytic myositis, particularly in the circular muscle. Steroid therapy resulted in clinical remission; cessation of steroids, in relapse. Further full-thickness biopsies showed an initial reduction in alpha-smooth muscle actin immunostaining in circular muscle myocytes and later atrophy and disappearance of many myocytes. Vascular and the remaining enteric smooth muscle cells showed HLA-DR and intercellular adhesion molecule 1 expression. These observations demonstrate the ability of enteric myocytes to take part in an inflammatory response and to change their phenotype, allowing them to act as antigen-presenting cells and to activate T cells. This and possible cytokine production by the myocytes play a role in their own destruction. This process responded to immunosuppressive therapy.