Pseudopseudohypoparathyroidism

A 13-year-old girl was notably short and had short fourth metacarpals and metatarsals. She was very mildly mentally retarded.

Levels of serum calcium were 2.44 mmol/L; phosphate, 1.68 mmol/L; alkaline phosphatase, 231 U/L, and parathyroid hormone, 4 pg/mL. Skull films showed calcification of the basal ganglia. Dr Alexander K. C. Leung of Calgary, Alberta, made the diagnosis of pseudopseudohypoparathyroidism.

Dr Leung comments that patients with pseudopseudohypoparathyroidism and patients with pseudohypoparathyroidism have the same clinical stigmata-short stature, short fourth metacarpals and metatarsals, round face, mild to moderate mental retardation, subcutaneous calcification, and calcification of the basal ganglia. However, persons with pseudohypoparathyroidism also have end-organ resistance to parathyroid hormone, and thus have hypocalcemia, hyperphosphatemia, and elevated parathyroid hormone levels. In contrast, patients such as this adolescent with pseudopseudohypoparathyroidism have normal serum calcium, phosphate, and parathyroid hormone levels.