Total knee arthroplasty in a patient with pseudopseudohypoparathyroidism.

Pseudopseudohypoparathyroidism (PPH) is a rare genetic disorder characterized by multiple musculoskeletal anomalies and normal serum calcium, phosphate, and parathyroid hormone levels. Although the musculoskeletal manifestations of PPH are well known, little has been reported on the management of orthopedic problems. We report a case of total knee arthroplasty (TKA) performed in a patient with PPH. To our knowledge, this case is not only unique to the arthroplasty literature but is the first report of its kind. This report illustrates the unique pathoanatomy of PPH, the medical and surgical management required, and a previously unreported musculoskeletal abnormality associated with PPH: synovial osteochondromatosis of the knee. Common musculoskeletal anomalies associated with PPH include shortening/bowing of long bones; shortening of metacarpals, metatarsals, and/or phalanges; exostoses; calcification/ossification of subcutaneous and/or periarticular soft tissues; a thickened calvarium; microcephaly; bony coalitions of the hand; vertebral column abnormalities; cubitus valgus; radius/ulna curvus; coxa vara; coxa valga; and genu valgum. This case is the first to report an association of synovial osteochondromatosis with PPH. Because synovial osteochondromatosis and PPH share a common disorder of soft tissue calcification/ossification, as well as abnormal bone formation, this clinical finding does not seem merely coincidental.