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McCune–Albright Syndrome
Published in Dongyou Liu, Tumors and Cancers, 2017
Besides somatic activating (gain-of-function) GNAS mutations in MAS, germline inactivating (loss-of-function) GNAS mutations are associated with multiple phenotypes. These include pseudopseudohypoparathyroidism (PPHP, due to an inactivating mutation of the paternal GNAS allele resulting in expression of the protein product Gsα only from the maternal allele), pseudohypoparathyroidism 1A (due to an inactivating mutation of the maternal GNAS allele resulting in expression of the protein product Gsα only from the paternal allele), pseudohypoparathyroidism IB (due to deletion of the regulatory differentially methylated region of the GNAS locus), and progressive osseous heteroplasia (POH; due possibly to an inactivating GNAS mutation of the paternal allele).
Metabolic and endocrine bone disorders
Published in Ashley W. Blom, David Warwick, Michael R. Whitehouse, Apley and Solomon’s System of Orthopaedics and Trauma, 2017
Pseudohypoparathyroidism is a rare genetic cause of hypocalcaemia in which peripheral sensitivity to PTH is impaired due to a loss of function mutation in the Gs alpha subunit of G proteins involved in mediating peripheral responses to PTH. In contrast to type II, types la and lb are both characterized by a defective urinary cyclic AMP response to PTH, which can be useful in confirming the diagnosis. Type Ia is associated with specific morphological features of Albright’s hereditary osteodystrophy such as short stature, short fourth and fifth metacarpals and sometimes mild mental retardation. Pseudopseudohypoparathyroidism refers to a condition characterized by similar phenotypic features of Albright’s hereditary osteodystrophy, but with normal calcium metabolism.
Practice Paper 7: Answers
Published in Anthony B. Starr, Hiruni Jayasena, David Capewell, Saran Shantikumar, Get ahead! Medicine, 2016
Anthony B. Starr, Hiruni Jayasena, David Capewell
Pseudohypoparathyroidism is an autosomal dominant condition characterized by end-organ resistance to PTH. Features include learning difficulties, short statute and short fourth and fifth metacarpals, accompanied by a low PTH, low calcium and high phosphate. Pseudopseudohypoparathyroidism describes the condition where all the phenotypic features of pseudohypoparathyroidism are present, in conjunction with a normal biochemistry.
Pseudohypoparathyroidism presenting in children at a tertiary hospital in Johannesburg, South Africa
Published in Journal of Endocrinology, Metabolism and Diabetes of South Africa, 2020
N Madi, FY Moosa, KB Parbhoo, JM Pettifor, K Thandrayen
Pseudopseudohypoparathyroidism (PPHP) and progressive osseous heteroplasia (POH) and osteoma cutis (OC) phenotypes are due to a lack of expression/function of Gsα, the difference being in the origin of the inactivating GNAS pathogenic variants. PPHP results from lack of expression of the paternal allele, while POH and OC can be associated with pathogenic variants in either the maternal or paternal allele. Individuals with PPHP have normal calcium and PTH levels with features of AHO and decreased Gsα activity. Individuals may also have intrauterine growth restriction, ectopic ossifications, obesity and intellectual disabilities. Individuals with OC have subcutaneous and dermal ossifications, while those with POH have ossifications that extend to the deep connective tissues.20
Pseudohypoparathyroidism type 1B – a rare cause of tetany: case report
Published in Paediatrics and International Child Health, 2018
Catarina Garcia, Cátia R. Correia, Lurdes Lopes
The heterozygous inactivating mutations involving GNAS exons cause different disorders. This is explained by genomic imprinting, an epigenetic phenomenon affecting a restricted number of genes by which one allele, either maternal or paternal, undergoes a partial or total loss of expression [9,11,13]. When the mutation occurs on the maternal allele, PHP-1A patients present with multihormonal resistance and AHO features. On the other hand, if an inactivating mutation is located on the paternal allele, patients will present with most of the AHO features but will not be obese or have neurocognitive impairment and usually no hormonal resistance, which is called pseudopseudohypoparathyroidism (PPHP) [23].