Pseudohypoparathyroidism presenting as renal osteodystrophy

Pseudohypoparathyroidism (pseudo HPT) is the prototype of a group of diseases with end organ unresponsiveness to parathyroid hormone (PTH). Patients with the classic form of this disease have both renal and osseous resistance to PTH. We describe a rare variant of pseudo HPT with classic renal unresponsiveness to PTH but normal skeletal responsiveness to this hormone. The latter patients develop mentabolic bone disease in response to depressed calcium and elevated PTH levels. Skeletal abnormalities are histologically and radiologically indistinguishable from renal osteodystrophy and these patients frequently present in childhood with symptoms relating to slipped capital femoral epiphyses. The latter radiologic findings, in the face of normal renal function or the classic somatic features of the syndrome, are highly suggestive of pseudo HPT with normal skeletal responsiveness to PTH.