Calcium pyrophosphate dihydrate deposition disease and familial hypomagnesemia.

A 40-year-old woman presented with calcium pyrophosphate synovitis and chondrocalcinosis. She was subsequently found to have hypomagnesemia, as did her 22-year-old son. Metabolic studies demonstrated normal gastrointestinal absorption of magnesium, and impaired renal conservation of magnesium without other evidence of renal tubular dysfunction. It seems likely that a genetically determined abnormality of magnesium metabolism was responsible for the occurrence of chondrocalcinosis in this patient.