Chapter 566 Pseudohypoparathyroidism (Albright Hereditary Osteodystrophy) Daniel A. Doyle In contrast to the situation in hypoparathyroidism, in pseudohypoparathyroidism (PHP) the parathyroid glands are normal or hyperplastic and they can synthesize and secrete parathyroid hormone (PTH). Serum levels of immunoreactive PTH are elevated even when the patient is hypocalcemic and may be elevated when the patient is normocalcemic. Neither endogenous nor administered PTH raises the serum levels of calcium or lowers the levels of phosphorus. The genetic defects in the hormone receptor adenylate cyclase system are classified into various types depending on the phenotypic and biochemical findings. Type Ia Type Ia accounts for the majority of patients with PHP. Affected patients have a genetic defect of the α subunit of the stimulatory guanine nucleotide-binding protein (Gsα). This coupling factor is required for PTH bound to cell surface receptors to activate cyclic adenosine monophosphate (cAMP). Heterogeneous mutations of the Gsα gene have been documented; the gene is located on chromosome 20q13.2. Deficiency of the Gsα subunit is a generalized cellular defect and accounts for the association of other endocrine disorders with type Ia PHP. The defect is inherited as an autosomal dominant trait, and the paucity of father-to-son transmissions is thought to be due to decreased fertility in males. Tetany is often the presenting sign. Affected children have a short, stocky build and a round face. Brachydactyly with dimpling of the dorsum of the hand is usually present. The 2nd metacarpal is involved least often. As a result, the index finger occasionally is longer than the middle finger. Likewise, the 2nd metatarsal is only rarely affected. There may be other skeletal abnormalities such as short and wide phalanges, bowing, exostoses, and thickening of the calvaria. These patients often have calcium deposits and metaplastic bone formation subcutaneously. Moderate degrees of mental retardation, calcification of the basal ganglia, and lenticular cataracts are common in patients whose disease is diagnosed late. Only gold members can continue reading. Log In or Register to continue Share this:Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window) Related Related posts: Other Viral Hemorrhagic Fevers Diphtheria (Corynebacterium diphtheriae) Musculoskeletal Pain Syndromes Embryology, Anatomy, and Function of the Esophagus Stay updated, free articles. Join our Telegram channel Join Tags: Nelson Textbook of Pediatrics Expert Consult Jun 18, 2016 | Posted by admin in PEDIATRICS | Comments Off on Pseudohypoparathyroidism (Albright Hereditary Osteodystrophy) Full access? Get Clinical Tree
Chapter 566 Pseudohypoparathyroidism (Albright Hereditary Osteodystrophy) Daniel A. Doyle In contrast to the situation in hypoparathyroidism, in pseudohypoparathyroidism (PHP) the parathyroid glands are normal or hyperplastic and they can synthesize and secrete parathyroid hormone (PTH). Serum levels of immunoreactive PTH are elevated even when the patient is hypocalcemic and may be elevated when the patient is normocalcemic. Neither endogenous nor administered PTH raises the serum levels of calcium or lowers the levels of phosphorus. The genetic defects in the hormone receptor adenylate cyclase system are classified into various types depending on the phenotypic and biochemical findings. Type Ia Type Ia accounts for the majority of patients with PHP. Affected patients have a genetic defect of the α subunit of the stimulatory guanine nucleotide-binding protein (Gsα). This coupling factor is required for PTH bound to cell surface receptors to activate cyclic adenosine monophosphate (cAMP). Heterogeneous mutations of the Gsα gene have been documented; the gene is located on chromosome 20q13.2. Deficiency of the Gsα subunit is a generalized cellular defect and accounts for the association of other endocrine disorders with type Ia PHP. The defect is inherited as an autosomal dominant trait, and the paucity of father-to-son transmissions is thought to be due to decreased fertility in males. Tetany is often the presenting sign. Affected children have a short, stocky build and a round face. Brachydactyly with dimpling of the dorsum of the hand is usually present. The 2nd metacarpal is involved least often. As a result, the index finger occasionally is longer than the middle finger. Likewise, the 2nd metatarsal is only rarely affected. There may be other skeletal abnormalities such as short and wide phalanges, bowing, exostoses, and thickening of the calvaria. These patients often have calcium deposits and metaplastic bone formation subcutaneously. Moderate degrees of mental retardation, calcification of the basal ganglia, and lenticular cataracts are common in patients whose disease is diagnosed late. Only gold members can continue reading. Log In or Register to continue Share this:Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window) Related Related posts: Other Viral Hemorrhagic Fevers Diphtheria (Corynebacterium diphtheriae) Musculoskeletal Pain Syndromes Embryology, Anatomy, and Function of the Esophagus Stay updated, free articles. Join our Telegram channel Join Tags: Nelson Textbook of Pediatrics Expert Consult Jun 18, 2016 | Posted by admin in PEDIATRICS | Comments Off on Pseudohypoparathyroidism (Albright Hereditary Osteodystrophy) Full access? Get Clinical Tree
