An autosomal dominant form (OMIM:603233) of pseudohypoparathyroidism*, which is characterised by PTH-resistant hypocalcaemia and hyperphosphataemia.
*A heterogeneous group of disorders characterised by resistance to parathyroid hormone
Clinical findings Patients with PHP1B lack developmental defects seen in Albright hereditary osteodystrophy, and their endocrinopathy is limited to PTH resistance.
Molecular pathology Defects of:
• GNAS, which encodes various proteins–depending on the splicing–involved in imprinting and regulating transcription
• STX1A, which encodes a syntaxin/target-SNAP receptor that allows specific synaptic vesicle docking and membrane fusion,
cause pseudohypoparathyroidism 1B