Calcification of the perineurium. A case report.

Necropsy of a patient who died of uremia complicating juvenile diabetes revealed selective calcification of the perineurial sheaths in the sciatic nerves. The calcium phosphate deposits were limited to the outer layers of the perineurium while the innermost lamellae were free. Structural analysis, including electron diffraction and X-ray microanalysis, showed electron-dense, spicular deposits, which were composed mainly of finely crystallized hydroxyapatite. The end-stage diabetic nephropathy of the patient was associated with an extremely high calcium phosphorus ion product known to favour metastatic calcification. The mechanism of the selective localization of the calcium phosphate deposits to the outer layers of the perineurial sheaths is discussed with reference to the structure and suggested barrier function of the perineurium in regard to phosphate ions.