Intraarticular Heterotopic Ossification as the Initial Manifestation in a Child with Pseudohypoparathyroidism 1a

Abstract

The authors describe a 6 year old girl who initially presented with limping due to intraarticular ossification of left knee joint but later developed carpopedal spasms. She had Albright's hereditary osteodystrophy phenotype with hypocalcemia and hyperphosphatemia with elevated parathyroid hormone. She was diagnosed to have pseudohypoparathyroidism 1a (PHP1a) with heterotopic intraarticular ossification. This case emphasizes the need for evaluation of PHP in patients with intraarticular ossification to facilitate early diagnosis of PHP.

Brief Review of Models of Ectopic Bone Formation

“…Ectopic bone formation is most often experimentally induced, but does also have clinical relevance. For example, ectopic bone has long been described as a congenital or inherited malformation [1][2][3][4], or a complication of various conditions such as paraplegia [5,6], posthip arthroplasty [7,8], postburn, or traumatic injury [9][10][11]. Such pathologic formation of endochondral bone in soft tissues such as muscle, subcutaneous tissue, and fibrous tissue adjacent to joints is called heterotopic ossification (HO).…”

Dynamic Balance between PTH1R-Dependent Signal Cascades Determines Its Pro- or Anti-Osteogenic Effects on MSC

“…For example, the intermittent action of PTH activates bone formation, while the constant introduction of PTH enhances the process of bone resorption and suppress osteogenesis. In hereditary diseases associated with impaired PTH receptor signaling, such as pseudohypoparathyroidism or progressive osteoid heteroplasia, foci of ectopic ossification or ectopic bone formation occur in the subcutaneous adipose tissue, respectively [ 25 , 26 , 27 ]. This phenomenon may be based on the heterogeneity of MSC responses in adipose and bone tissues.…”