Perineurial cell hyperplasia in early-onset polyneuropathy with multiple cranial neuropathies.

We describe a patient who as a teenager developed a sensory-motor polyneuropathy with optic atrophy. Over the next three decades, multiple cranial neuropathies appeared. Striking areas of subperineurial cellular proliferation were observed on sural nerve biopsy. The ultrastructural and immunohistochemical characteristics of these aggregates were those of perineurial cell hyperplasia. To our knowledge, this is the second full report associating perineurial cell hyperplasia with a sensory-motor polyneuropathy and the first in the English literature.