Myopathy of internal anal sphincter with polyglucosan inclusions.

In two members of an affected family with a hereditary syndrome of proctalgia fugax and constipation, a hypertrophied internal anal sphincter was found with histological features suggesting a myopathy of this muscle. In these two patients, and in an unrelated patient with a similar clinical syndrome, smooth muscle fibres of the internal anal sphincter showed numerous vacuoles, many of which contained ovoid inclusion bodies. The structural features and histochemical reactions of the inclusion bodies were consistent with a polyglucosan composition. Histological examination of the internal anal sphincter may reveal smooth muscle abnormalities in functional bowel disorders.