Polyneuropathy with osmiophilic membrane-bound, cytoplasmic inclusions in Schwann cells (POMCIS)

In the cytoplasm of Schwann cells of a sural nerve biopsy from a 21-year-old female patient with chronic neuropathy we noted numerous unique, usually double membrane-bound, osmiophilic, granular or globular inclusions, approximately 30-600 microm in diameter. Some of these membrane-bound vesicular or tubular structures contained less dense or no osmiophilic inclusions. Morphometry revealed a reduction of the myelin area per endoneural area to approximately 13% (normal value: 20- 30%) and of the density of myelinated nerve fibers to 5,412/mm(2) (normal value at this age: 6,000-9,000/mm(2)). Large myelinated nerve fibers were predominantly reduced in number, and no myelinated nerve fibers with diameters larger than 4.5 microm were seen. Numerous, usually small onion bulb formations indicated a predominantly demyelinating type of neuropathy. This is to the best of our knowledge the first case of a chronic demyelinating neuropathy in which this kind of presumably pathognostic deposits in the cytoplasm of Schwann cells was detected.