A rare autosomal dominant condition (OMIM:612463) characterised by response to PTH accompanied by changes of Albright hereditary osteodystrophy.
Clinical findings Albright hereditary osteodystrophy–short stature, obesity, round facies, subcutaneous ossifications, brachydactyly, other skeletal anomalies, and bone manifestations of pseudohypoparathyroidism.
Lab Normal serum Ca2+ and phosphorus.
Both the pseudo- and pseudo-pseudo forms may occur in the same kindred. The pseudo form is resistant to PTH and is characterised by a loss of function mutation of the Gs-alpha isoform of GNAS gene on the maternal allele–i.e., the Gs-alpha protein is only expressed from the paternal allele. The pseudo-pseudo form is characterised by a loss of function mutation of the Gs-alpha isoform of GNAS on the paternal allele–i.e., the Gs-alpha protein is only expressed from the maternal allele. GNAS encodes a stimulatory G-protein alpha subunit, and key component of the classical signal transduction pathway linking receptor-ligand interactions to adenylyl cyclase activation and various cellular responses, cause pseudo-pseudo-hypoparathyroidism.
Synonym Albright hereditary osteodystrophy without multiple hormone resistance