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Indian Dermatology Online Journal 2023
PubMed: 37266104
DOI: 10.4103/idoj.idoj_321_22 -
Clinical Genetics Sep 2023The GNAS locus is an imprinted site. The α-subunit of the stimulatory G protein (Gsα) and extralarge variant (XLαs) are the two important products of the GNAS locus.... (Review)
Review
The GNAS locus is an imprinted site. The α-subunit of the stimulatory G protein (Gsα) and extralarge variant (XLαs) are the two important products of the GNAS locus. The abnormal expression of Gsα is associated with pseudohypoparathyroidism (PHP) and related disorders, including Albright hereditary osteodystrophy (AHO), pseudopseudohypoparathyroidism (PPHP), and progressive osseous heteroplasia (POH). XLαs protein can mimic the catalytic intracellular synthesis of cyclic adenosine monophosphate (cAMP) by Gsα in response to parathyroid hormone (PTH) stimulation, which may be involved in the pathogenesis of PPHP and POH in patients with paternal GNAS defects. A paternally inherited nonsense variant in the first exon of XLαs in an adult patient may be associated with fractures and osteopetrosis. The relationship between the XLαs product of the GNAS locus and bone remodeling may have been overlooked. Here, we summarize the phenotypes of genetic mouse models and clinical cases of XLαs variations and suggest that the abnormal paternal expression of XLαs may be associated with the development of POH and affect osteoblast and osteoclast differentiation.
Topics: Humans; Animals; Mice; Bone Density; Chromogranins; GTP-Binding Protein alpha Subunits, Gs; Pseudohypoparathyroidism; Mutation
PubMed: 37249323
DOI: 10.1111/cge.14378 -
BMC Musculoskeletal Disorders Mar 2023Progressive osseous heteroplasia (POH) is a rare genetic condition that causes progressive ossification. This usually results from an inactivating mutation of the...
BACKGROUND
Progressive osseous heteroplasia (POH) is a rare genetic condition that causes progressive ossification. This usually results from an inactivating mutation of the paternal GNAS gene. Herein, we report a case of POH caused by a novel mutation in exon 2 of the GNAS gene.
CASE PRESENTATION
A 5-year-old Chinese boy was referred to our hospital for a growing mass in his right foot. Although laboratory findings were normal, radiographic imaging revealed severe ossification in his right foot and smaller areas of intramuscular ossification in his arms and legs. A de novo mutation (c.175C > T, p.Q59X) in exon 2 of the GNAS gene was identified, prompting a diagnosis of POH. We conducted a systematic literature review to better understand this rare disease.
CONCLUSION
We have discovered that a de novo nonsense mutation in exon 2 of GNAS can lead to POH. Our literature review revealed that ankylosis of the extremities is the primary clinical outcome in patients with POH. Unlike other conditions such as fibrodysplasia ossificans progressiva (FOP), patients with POH do not experience respiratory failure. However, much remains to be learned about the relationship between the type of GNAS gene mutation and the resulting POH symptoms. Further research is needed to understand this complex and rare disease. This case adds to our current understanding of POH and will contribute to future studies and treatments.
Topics: Male; Humans; Child, Preschool; GTP-Binding Protein alpha Subunits, Gs; Rare Diseases; Ossification, Heterotopic; Myositis Ossificans; Exons; Mutation; Chromogranins
PubMed: 37003989
DOI: 10.1186/s12891-023-06371-4 -
Zhonghua Bing Li Xue Za Zhi = Chinese... Apr 2023
Topics: Humans; Ossification, Heterotopic; Skin Diseases, Genetic; Bone Diseases, Metabolic
PubMed: 36973211
DOI: 10.3760/cma.j.cn112151-20221104-00918 -
Clinical and Experimental Dermatology Jun 2023
Topics: Humans; Scalp; Skin Diseases, Genetic; Ossification, Heterotopic; Alopecia; Skin Neoplasms
PubMed: 36897160
DOI: 10.1093/ced/llad087 -
JAAD Case Reports Mar 2023
PubMed: 36873053
DOI: 10.1016/j.jdcr.2023.01.010 -
European Journal of Dermatology : EJD Nov 2022
Topics: Humans; Bone Diseases, Metabolic; Skin Diseases, Genetic
PubMed: 36856402
DOI: 10.1684/ejd.2022.4386 -
Journal of Cutaneous Pathology Apr 2023
Topics: Humans; Pseudohypoparathyroidism; Bone Diseases, Metabolic; Skin Diseases, Genetic; Ossification, Heterotopic
PubMed: 36691934
DOI: 10.1111/cup.14397 -
Calcified Tissue International Apr 2023Progressive osseous heteroplasia (POH) is a rare, debilitating disorder characterized by heterotopic ossification in the skin and muscles, resulting in contractures of...
INTRODUCTION
Progressive osseous heteroplasia (POH) is a rare, debilitating disorder characterized by heterotopic ossification in the skin and muscles, resulting in contractures of the joints and progressive loss of function. While 60-70% of the POH patients have paternally inherited, inactivating pathogenic variants in GNAS, the remaining 30-40% have no known etiology. FAM111B pathogenic variants, located on chromosome 11q12.1, cause POIKTMP (hereditary fibrosing poikiloderma with tendon contractures, myopathy, and pulmonary fibrosis), a very rare, autosomal-dominant disorder with high frequency of de novo missense pathogenic variants, which affects multiple tissues and organs, causing extensive fibrosis and muscle adiposis, though the exact mechanism is unknown. To our knowledge, there are no reports of FAM111B associated with POH. We describe the first case of POH phenotype associated with a novel de novo frameshift pathogenic variant in the FAM111B and present an analysis of the protein structure and function caused by this genomic disruption.
CASE
A 15-year-old African-American male presented with generalized calcific nodules, progressive contractures, and muscle weakness leading to immobility, beginning at 6 years of age. Cutaneous examination showed generalized hard nodules varying from small to plaque-like ulcerated erupted skin lesions. Biochemical evaluation revealed 25(OH) vitamin D insufficiency (20 ng/mL), and normal levels of parathyroid hormone, FGF-23, alkaline phosphatase, calcium, and phosphorus. Skeletal survey radiographs and computed tomography (CT) of the chest, abdomen, and pelvis showed extensive soft tissue and muscle heterotopic ossifications involving shoulders, axillae, trunk, abdomen, pelvis, upper and lower extremities, in a clumped, conglomerate distribution within muscle, subcutaneous fat, and in some areas extending to the skin. There was no pulmonary fibrosis on the chest CT. The clinical and radiographic findings were most consistent with POH. A trio-clinical exome sequencing revealed a de novo heterozygous likely pathogenic variant in the FAM111B (OMIM # 615584) (c.1462delT [p.Cys488Valfs*21]). The resulted frameshift change in exon 4 replaced C-terminal region with 21 alternative amino acids. Multiple, previously reported disease-associated variants appear to localize within the trypsin-like cysteine/serine peptidase domain in which this variant occurs, supporting the functional significance of this region, though none have been previously reported to be associated with POH phenotype. Our 3D protein modeling showed obliteration of predicted protein folding and structure, and elimination of the zinc-binding domain, likely severely affecting protein function.
CONCLUSION
This is the first case of POH phenotype associated with a novel de novo pathogenic frameshift variant in FAM111B. Whether the frameshift change in FAM111B predicts POH remains unclear. Further evaluations are necessary to fully elucidate this finding and the potential role and mechanism by which the FAM111B variants contributes to POH phenotype.
Topics: Male; Humans; GTP-Binding Protein alpha Subunits, Gs; Ossification, Heterotopic; Phenotype; Contracture; Fibrosis; Cell Cycle Proteins
PubMed: 36575358
DOI: 10.1007/s00223-022-01053-0