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McCune−Albright Syndrome
Published in Dongyou Liu, Handbook of Tumor Syndromes, 2020
Besides somatic activating (gain-of-function) GNAS mutations seen in MAS, germline inactivating (loss-of-function) GNAS mutations contribute to multiple phenotypes, ranging from pseudohypoparathyroidism (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), to progressive osseous heteroplasia (POH; due possibly to an inactivating GNAS mutation of the paternal allele) [19,20].
Pseudohypoparathyroidism
Published in Pallavi Iyer, Herbert Chen, Thyroid and Parathyroid Disorders in Children, 2020
Ambika P. Ashraf, Todd D. Nebesio
Categories of PHP and related disorders: PHP type 1A (PHP1A): heterozygous inactivating mutation in the GNAS gene encoding for Gsα is the most common cause of PHP. Loss of maternal imprinting (lack of expression of maternal allele) leads to defective function of Gsα in the target tissues that has maternal tissue-specific imprinting (e.g., proximal renal tubules [PTH], pituitary gland [GHRH], gonads [LH/FSH], and thyroid [TSH]). Features of Albright hereditary osteodystrophy (AHO) are common in PHP1A.PHP type 1B (PHP1B): abnormal patterns of methylation (loss of imprinting) in the differentially methylated regions (DMR) associated with GNAS complex locus at the maternal exon (GNAS A/B: TSS-DMR). There is also a paternal-specific imprinting pattern of GNAS DMR on both alleles resulting in a clinical phenotype characterized by renal resistance to PTH and mild resistance to TSH in the absence of other endocrine or physical abnormalities (no AHO features) and normal Gsα activity.PHP type 1C (PHP1C): lack of expression of maternal allele and characterized by multi-hormone resistance and the presence of signs of AHO. Normal Gsα activity. Considered a variant of PHP type 1A.Pseudopseudohypoparathyroidism (PPHP): paternally derived inactivating mutations in GNAS gene (lack of expression of paternal allele). AHO phenotype occurs in the absence of endocrine abnormalities.Progressive osseous heteroplasia (POH): paternally inherited GNAS inactivating mutations. Characterized by ectopic bone formation in dermis, skeletal muscle, and deep connective tissues. No PTH resistance.Genetic alterations within PRKAR1A and PDE4D: heterozygous point mutations in either gene cause acrodysostosis (brachydactyly involving all phalanxes, metacarpals, and metatarsals), nasal hypoplasia, facial dysostosis, and variable hormone resistance (e.g., PTH and TSH).PHP type 2 (PHP2): molecular defect has not been identified.
Long-term radial extracorporeal shock wave therapy for neurogenic heterotopic ossification after spinal cord injury: A case report
Published in The Journal of Spinal Cord Medicine, 2022
Yun Li, Yulan Zhu, Zhen Xie, Congyu Jiang, Fang Li
However, the specific mechanism of RSWT on treating HO still remains unclear. It is hypothesized that RSWT generates oscillations in the tissue which improves the microcirculation and metabolic activity and results in cavitation-induced microinjury, leading to pain reduction and neovascularization.11,20 In this case, we firstly observed a reduction in NHO lesion during the process of RSWT intervention. During HO maturation, spontaneous bone mass resolution is possible, like normal bone remodeling, can occur in children with progressive osseous heteroplasia.21 It is still common in adults that the ossification increases gradually and tends to stabilize. So far, the only disease which has been certified that the size of the lesion could be reduced by RSWT is calcifying tendinitis of the shoulder.22,23,24 It is speculated that the pressure of the shock waves may cause fragmentation and cavitation inside the calcifications, leading to the disintegration of the deposits, which may be resorbed in the surrounding soft tissues locally by phagocytosis. Therefore, whether RSWT reduces the ossification mass and exerts similar mechanical effect on HO is needed to be further explored.
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