Syndrome of diffuse abnormal insertional activity: case report and family study.

In 1979 Wiechers and Johnson described ten patients with diffuse abnormal insertional activity on EMG examination in the absence of neuromuscular disease. We present a family group with identical findings. The propositus is a 53-year-old woman who presented with back pain. EMG studies revealed trains of positive sharp waves with needle movement in all muscles studied. Nerve conduction studies, radiographs, and laboratory studies were all unremarkable. We recruited eight additional family members who underwent a screening EMG of five muscles. Four patients had trains of positive sharp waves present in all five muscles. To our knowledge, this is the first report confirming the findings of Wiechers and Johnson. We concur with them that the abnormality appears to be genetically transmitted in an autosomal dominant pattern. Although without clinical significance, it is important for electromyographers to be aware of this entity so as not to mistakenly ascribe serious neuromuscular disease to these patients.