Pseudohypoparathyroidism type 1c (PHP1c) is a rare type of pseudohypoparathyroidism (PHP; see this term) characterized by resistance to parathyroid hormone (PTH) and other hormones, which manifests with hypocalcemia, hyperphosphatemia and elevated PTH levels, a constellation of clinical features collectively termed Albright's hereditary osteodystrophy (AHO; see this term), but normal activity of the stimulatory protein G (Gs alpha).
The prevalence is unknown.
Clinical manifestations of PHP1c are similar to those seen in pseudohypoparathyroidism type 1a (PHP1a; see this term). They display the symptoms and signs of AHO (brachydactyly (most often the shortening of the 3, 4 and 5th metacarpals), rounded face, short stature, central obesity, subcutaneous ossifications and variable development delay) as well as PTH-resistance leading to hypocalcemia and hyperphosphatemia, and resistance towards TSH and, sometimes, other hormones.
The exact etiology is unknown as mutations in the GNAS gene (20q13) are only rarely found. Other components of the cAMP-dependent signaling pathway, such as adenylyl cyclase, inhibitory G proteins, or phosphodiesterases might be impaired.
In familial cases the disease is inherited autosomal dominantly and genetic counseling is possible.
Last update: October 2014