Ectopic ossification in the cranial dura mater in dialysis patients with secondary hyperparathyroidism.

We report the case of a 69-year-old woman with secondary hyperparathyroidism who underwent maintenance haemodialysis therapy for 17 years and who presented with severe dural calcification and right subdural haematoma. Her dura mater displayed a rock barnacle-like appearance, and cerebral superficial arteries adhered to the sclerotic lesions. On the microscopic observation, calcified tissue with a clear lamellar structure and osteopontin immunoreactivity was observed. Tartrate-resistant acid phosphatase immunoreactive polynucleated giant cells infiltrated around the tissue. Such morphological properties are specific to the calcified tissue formed through a bone formation-like mechanism that is often observed in arterial media in patients with chronic kidney disease.