Granular nuclear inclusion body disease: fine structure of tibial muscle and sural nerve.

Fine granular (hyaline) intranuclear inclusion bodies were found in perivascular cells of a muscle and a sural nerve biopsy from a 32-year-old woman with slowly progressive motor disturbances. The hyaline nuclear inclusion bodies could be distinguished from other intranuclear hyaline inclusions by their granularity, the size of the granules (approximately 5-15 nm), and the positive iron staining reaction. They were not seen in muscle fibers or Schwann cells. Because of these apparently pathognomonic structural features the patient appears to present a condition that has not been described before.