pseudohypoparathyroidism type 1B
pseudohypoparathyroidism type 1BA form (OMIM:603233) of pseudohypoparathyroidism, a heterogeneous group of disorders characterised by resistance to parathyroid hormone, which is characterised by PTH-resistant hypocalcaemia and hyperphosphataemia. Patients with PHP1B lack developmental defects seen in Albright hereditary osteodystrophy, and their endocrinopathy is limited to PTH resistance.
Pseudohypoparathyroidism type 1B is caused by defects of:
(1) STX1A, which encodes a syntaxin/target-SNAP receptor that allows specific synaptic vesicle docking and membrane fusion; and
(2) GNAS, which encodes various proteins—depending on the splicing—involved in imprinting and regulating transcription.