Identification of a novel GNAS mutation in a case of pseudohypoparathyroidism type 1A with normocalcemia

GNAS locus: bone related diseases and mouse models

GNASis a complex locus characterized by multiple transcripts and an imprinting effect. It orchestrates a variety of physiological processes via numerous signaling pathways. Human diseases associated with the GNAS gene encompass fibrous dysplasia (FD), Albright's Hereditary Osteodystrophy (AHO), parathyroid hormone(PTH) resistance, and Progressive Osseous Heteroplasia (POH), among others. To facilitate the study of the GNAS locus and its associated diseases, researchers have developed a range of mouse models. In this review, we will systematically explore the GNAS locus, its related signaling pathways, the bone diseases associated with it, and the mouse models pertinent to these bone diseases.

Rare Case of Pseudohypoparathyroidism With Normocalcemia Because of a Novel GNAS Mutation

PTH resistance is characterized by hypocalcemia and hyperphosphatemia in the presence of elevated PTH concentrations, resulting in pseudohypoparathyroidism, which is subdivided into different types according to its different pathogenesis and phenotype. PTH receptor is the alpha subunit of stimulatory G protein (Gsα)-coupled receptor. Pathogenic variants of GNAS gene, encoding for Gsα, lead to reduced Gsα function and PTH resistance. We report a patient with PHP type 1a, with no documented evidence of hypocalcemia, presenting with AHO phenotype and multihormone resistance to PTH, TSH, and GnRH. Her genetic testing showed a novel heterozygous pathogenic variants, a c.934T > G change in exon 11 in adenylate cyclase stimulatory G protein that has not been reported in the literature so far.

Central Precocious Puberty in a Boy with Pseudohypoparathyroidism Type 1A due to a Novel GNAS Variant, with Congenital Hypothyroidism as the First Manifestation

Pseudohypoparathyroidism (PHP) type 1A (PHP1A) is a disorder of multiple hormone resistance, mainly parathyroid hormone. It is associated with Albright hereditary osteodystrophy phenotypes. Patients with PHP1A may initially present with hypothyroidism during infancy and later develop typical PHP1A characteristics during their childhood. Central precocious puberty (CPP) is extremely rare among PHP1A patients in whom gonadotropin resistance is more usual. This is a case report of a 9.5-year-old boy with congenital hypothyroidism who developed hypocalcemia secondary to PHP. He had relatively short stature with height standard deviation score of -0.9. Obesity had been noted since the age of two years. At the presentation of PHP, pubertal-sized testes of 10 mL were observed, and CPP was documented with serum testosterone concentration of 298 ng/dL (normal for Tanner stage III, 100-320), luteinizing hormone of 3.9 IU/L (normal, 0.2-5.0), and follicle stimulating hormone of 4.8 IU/L (normal, 1.2-5.8). Pituitary magnetic resonance imaging was unremarkable. Genetic analysis confirmed the diagnosis of PHP1A with a novel heterozygous missense variant of GNAS gene in exon 13, c.1103A>G (p.Asp368Gly). Awareness of PHP1A diagnosis in patients with congenital hypothyroidism and early childhood-onset obesity is important for early diagnosis. Apart from multiple hormone resistance, CPP may manifest in patients with PHP1A.

GNAS mutation is an unusual cause of primary adrenal insufficiency: a case report

Background

Primary adrenal insufficiency in children has non-specific and extensive clinical features, so the diagnosis of its etiology is complex and challenging. Although congenital adrenal hyperplasia is the most common cause, more and more other genetic causes have been identified. GNAS mutation is easily overlooked as a rare cause of primary adrenal insufficiency. Here we firstly report a neonatal case of primary adrenal insufficiency caused by GNAS mutation.

Case presentation

A boy was diagnosed with congenital hypothyroidism 10 days post-partum and treated immediately. He also had persistent hyperkalaemia and hyponatraemia with elevated adrenocorticotropic hormone. At 70 days after birth, he was transferred to our hospital on suspicion of congenital adrenal hyperplasia. Physical examination found no other abnormalities except for growth retardation. Laboratory examination revealed increased aldosterone and normal cortisol, 17-hydroxyprogesterone, and androstenedione levels. Abnormally elevated parathyroid hormone was accompanied by normal blood calcium. Genetic assessment found a de novo, heterozygous c.432 + 1G > A variant in GNAS.

Conclusions

We report this case to highlight that GNAS mutation is an unusual cause of primary adrenal insufficiency. The combination of primary hypothyroidism and /or pseudohypoparathyroidism will provide diagnostic clues to this condition.

Pseudohypoparathyroidism Type 1A with Normocalcaemia, due to the Novel C.389A>G Variant of Exon 5 of the Guanine Nucleotide-Binding Protein, α-Stimulating Gene

Pseudohypoparathyroidism type 1A (PHP1A) is a rare disease caused by molecular defects in the maternally-inherited allele of the guanine nucleotide-binding protein, α-stimulating (GNAS) gene. The GNAS gene encodes the stimulatory G-protein α-subunit that regulates production of the second messenger cyclic adenosine monophosphate. Heterozygous inactivating mutations in these specific loci are responsible for a spectrum of phenotypic characteristics of the disease, including clinical features of the Albright’s hereditary osteodystrophy, due to resistance to parathyroid hormone (PTH). We report a case of PHP1A and explore the underlying novel point mutation of the GNAS gene that leads to an atypical PHP1A phenotype. A male patient with a round face, short stature, and brachydactyly accompanied by normocalcaemia and mild PTH resistance consulted at our center. The GNAS encoding region from the patient and both of his parents were amplified and sequenced directly in a sample of peripheral blood leukocytes. A novel c.389A>G point mutation in exon 5 of the GNAS gene, resulting in a p.Tyr130Cys peptidic chain change of the Gsα protein, detected in the proband, in heterozygous state. Sequencing of the GNAS gene from his parents did not reveal the c.389A>G mutation, confirming a de novo proband genotype. The maternal origin of the affected GNAS allele, along with mild PTH resistance, confirmed the PHP1A diagnosis. PHP1A, caused by inactivating GNAS mutations, presents a range of complex clinical phenotypes. The novel c.389A>G GNAS mutation presented in this case expands the spectrum of known PHP1A molecular defects and describes the associated phenotype.

A novel GNAS mutation inherited from probable maternal mosaicism causes two siblings with pseudohypoparathyroidism type 1A

Objectives Objectives Pseudohypoparathyroidism type 1A (PHP1A) is caused by maternal inheritance of GNAS mutations. It is characterized by the resistance to several hormones, primarily the parathyroid hormone (PTH), and the features of Albright's hereditary osteodystrophy. Case presentation Here, we present a family comprised two affected brothers with PHP1A and identify a novel mutation (c.277C>T) in the GNAS gene. The siblings developed a slightly different presentation in the same clinical condition. Although both patients presented with PTH resistance, which is the hallmark of PHP, the proband showed the thyroid-stimulating hormone resistance with the progression of heterotopic ossification from skin and subcutaneous tissue into deep connective tissue, while the younger brother with normocalcemia did not show the resistance to other hormones. The patients may inherit the mutation from their mother who presumably carries the mutation as a mosaicism. Conclusions Our case highlights the significance of considering mosaicism as an explanation for apparent de novo cases of pseudohypoparathyroidism.