Demyelinating changes in sural nerve biopsy of patients with HTLV-I-associated myelopathy.

We describe the sural nerve pathology in 3 patients with HTLV-I-associated myelopathy (HAM). These patients showed remarkable symptoms of myelopathy and had high HTLV-I titers in the serum and CSF. The common pathologic findings in the sural nerves were as follows: slightly decreased density in myelinated fibers (6,567/mm2, 6,488/mm2, and 7,159/mm2; control 9,999 +/- 3,446/mm2), frequent occurrence of demyelinated and remyelinated fibers, and many degenerating fibers with globule-like myelin changes. Teased-fiber analysis indicated the globule-like changes (Dyck's G change) to be accompanied by the formation of adjacent demyelinated segments. The globules result from slowly repetitive degenerative changes of myelin and are considered to be a form of demyelination. However, they have seldom been found in other demyelinating neuropathies, indicating the demyelination process with globule formation in HAM to be rather specific for this disease.