Cutaneous ossification in Albright's hereditary osteodystrophy

A 23-year-old woman presented with subcutaneous ossification, which together with short stature, stocky physique, round face and brachydactyly suggested Albright's hereditary osteodystrophy (AHO). Serum calcium and phosphorus levels were normal. AHO refers to the phenotype of the syndromes of pseudo-hypoparathyroidism (PHP) type Ia and pseudopseudohypoparathyroidism (PPHP), both considered genetically related variants with a defect of the alpha subunit of the stimulatory G protein of adenylate cyclase, necessary for the action of parathyroid and other hormones using cyclic AMP as an intracellular second messenger. PPHP differs from PHP in that it lacks parathyroid hormone resistance manifesting itself as hypocalcemia. Other endocrine end organ unresponsiveness, e.g. hypothyroidism and hypogonadism, may also be found with PHP. Both PHP and PPHP usually exhibit characteristic phenotypic abnormalities, of which subcutaneous ossification may be a presenting feature. The differential diagnosis of cutaneous calcification and ossification is outlined