Is the sensory neuropathy in ataxia-telangiectasia distinguishable from that in Friedreich's ataxia? Morphometric and ultrastructural study of the sural nerve in a case of Louis Bar syndrome.

The bioptical morphometric and ultrastructural study of sural nerve in a 17-year-old boy with ataxia-telangiectasia (AT) is reported. Our findings include a loss of fibers, particularly of large ones, axonal degenerative changes, Schwann cell inclusions of various type, and rare signs of primary demyelination. Teased-fiber study showed paranodal myelin enlargements, segmental demyelination, shortening, and/or variability of internodal length. This picture is similar to that in Friedreich's ataxia (FA), although they differ in degree and time of onset. A correct neuropathologic diagnosis of AT cannot be made on the basis of sural nerve biopsy alone.