A novel mutation causing pseudohypoparathyroidism 1A with congenital hypothyroidism and osteoma cutis

Early Diagnosis of Pseudohypoparathyroidism before the Development of Hypocalcemia in a Young Infant

Pseudohypoparathyroidism (PHP) is a rare, heterogeneous disorder characterized by end-organ resistance to parathyroid hormone (PTH). PTH resistance causes elevated PTH levels, hypocalcemia, and hyperphosphatemia. Since hypocalcemia causes life-threatening events, early diagnosis is crucial. However, the diagnosis of PHP is elusive during infancy because PHP is usually diagnosed with hypocalcemia-induced symptoms, which develop later in childhood when calcium requirements increase. A 1-month-old girl was referred to our clinic for elevated thyroid-stimulating hormone (TSH) levels on newborn screening. When measured 1 month after levothyroxine treatment, her TSH level normalized. At 4-months-old, multiple hard nodules were noted on her trunk. A punch skin biopsy revealed osteoma cutis associated with Albright’s hereditary osteodystrophy, a major characteristic of PHP. We performed targeted sanger sequencing of the GNAS gene and detected a heterozygous variant c.150dupA (p.Ser51Ilefs*3) in both the proband and her mother, causing frameshift and premature termination mutations. The patient was diagnosed with PHP Ia when she had normal calcium, phosphorous, and PTH levels. We report the early diagnosis of PHP Ia without hypocalcemia. It emphasizes the importance of meticulous physical examination in patients with congenital hypothyroidism.

Pseudohypoparathyroidism with Ectopic Calcification and 22q11 Deletion Syndrome: A Rare Case

Ectopic calcification in soft tissue is associated with several disorders including pseudohypoparathyroidism (PHP), which is characterized by resistance or nonresponse to parathyroid hormone (PTH) function. Association between PHP and 22q11DS, also known as DiGeorge syndrome, is rare, especially in children. We describe a newborn girl diagnosed with 22q11DS, presenting ectopic calcifications in soft tissue and suspicion of PHP. PTH function showed values close to the upper limit of the reference value. Radiology showed bone callus in the right wrist. PHP can be a new clinical finding associated with 22q11DS. Parathyroid function investigation in individuals with 22q11DS, presenting bone dysmorphisms and/or calcium metabolism alterations, should be considered.

Pseudohypoparathyroidism

Pseudohypoparathyroidism (PHP) refers to a heterogeneous group of uncommon, yet related metabolic disorders that are characterized by impaired activation of the Gsα/cAMP/PKA signaling pathway by parathyroid hormone (PTH) and other hormones that interact with Gsa-coupled receptors. Proximal renal tubular resistance to PTH and thus hypocalcemia and hyperphosphatemia, frequently in presence of brachydactyly, ectopic ossification, early-onset obesity, or short stature are common features of PHP. Registries and large cohorts of patients are needed to conduct clinical and genetic research, to improve the still limited knowledge regarding the underlying disease mechanisms, and allow the development of novel therapies.

Cognitive and behavioral phenotype of children with pseudohypoparathyroidism type 1A

Pseudohypoparathyroidism 1A (PHP1A) is a rare, genetic disorder. Most patients with PHP1A have cognitive impairment but this has not been systematically studied. We hypothesized that children with PHP1A would have lower intelligent quotient (IQ) scores than controls. To evaluate cognition and behavior, we prospectively enrolled children with PHP1A, one unaffected sibling (when available) and controls matched on BMI/age/gender/race. Evaluations included cognitive and executive function testing. Parents completed questionnaires on behavior and executive function. We enrolled 16 patients with PHP1A, 8 unaffected siblings, and 15 controls. Results are presented as mean (SD). The PHP1A group had a composite IQ of 85.9 (17.2); 25% had a composite IQ < -2 SD. The PHP1A group had significantly lower IQs than matched controls (composite IQ -17.3, 95%CI -28.1 to -6.5, p < 0.01) and unaffected siblings (composite IQ -21.5, 95%CI -33.9 to -9.1, p < 0.01). Special education services were utilized for 93% of the patients with PHP1A. Deficits were observed in executive function and parents reported delayed adaptive behavior skills and increased rates of attention deficit hyperactivity disorder. In conclusion, children with PHP1A have lower intelligence quotient scores, poorer executive function, delayed adaptive behavior skills, and increased behavior problems.

Progressive Development of PTH Resistance in Patients With Inactivating Mutations on the Maternal Allele of GNAS

CONTEXT

Parathormone (PTH) resistance is characterized by hypocalcaemia, hyperphosphatemia, and elevated PTH in the absence of vitamin D deficiency. Pseudohypoparathyroidism type 1A [PHP1A, or inactivating parathormone (PTH)/PTHrp signaling disorder 2, according to the new classification (iPPSD2)], is caused by mutations in the maternal GNAS allele.

OBJECTIVE

To assess PTH resistance over time in 20 patients affected by iPPSD2 (PHP1A), diagnosed because of family history, ectopic ossification, or short stature, and carrying a GNAS mutation.

METHODS

We gathered retrospective data for calcium, phosphate, thyrotropin (TSH), and PTH levels at regular intervals. PTH infusion testing (teriparatide) was performed in 1 patient.

RESULTS

Patients were diagnosed at a mean age of 3.9 years and had a mean follow-up of 2 years. TSH resistance was already present at diagnosis in all patients (TSH, 13.3 ± 9.0 mIU/L). Over time, PTH levels increased (179 to 306 pg/mL; P < 0.05), and calcium levels decreased (2.31 to 2.21 mmol/L; P < 0.05), but phosphate levels did not decrease with age as expected for healthy individuals. One patient born with ectopic ossifications showed an increase in cyclic adenosine monophosphate upon PTH infusion, similar to that of controls, at 7 months of age, but an impaired response at 4 years of age.

CONCLUSIONS

In patients with iPPSD2 (PHP1A), PTH resistance and hypocalcemia develop over time. These findings highlight the importance of screening for maternal GNAS mutations in the presence of ectopic ossifications or family history, even in the absence of PTH resistance and hypocalcemia. The follow-up of these patients should include regular assessments of calcium, phosphate, and PTH levels.

Identification of a novel mutation in a patient with pseudohypoparathyroidism type Ia

Pseudohypoparathyroidism type Ia (PHP Ia) is a disorder characterized by multiform hormonal resistance including parathyroid hormone (PTH) resistance and Albright hereditary osteodystrophy (AHO). It is caused by heterozygous inactivating mutations within the Gs alpha-encoding GNAS exons. A 9-year-old boy presented with clinical and laboratory abnormalities including hypocalcemia, hyperphosphatemia, PTH resistance, multihormone resistance and AHO (round face, short stature, obesity, brachydactyly and osteoma cutis) which were typical of PHP Ia. He had a history of repeated convulsive episodes that started from the age of 2 months. A cranial computed tomography scan showed bilateral calcifications in the basal ganglia and his intelligence quotient testing indicated mild mental retardation. Family history revealed that the patient's maternal relatives, including his grandmother and 2 of his mother's siblings, had features suggestive of AHO. Sequencing of the GNAS gene of the patient identified a heterozygous nonsense mutation within exon 11 (c.637 C>T). The C>T transversion results in an amino acid substitution from Gln to stop codon at codon 213 (p.Gln213^*). To our knowledge, this is a novel mutation in GNAS.

Postnatal establishment of allelic Gαs silencing as a plausible explanation for delayed onset of parathyroid hormone resistance owing to heterozygous Gαs disruption

Pseudohypoparathyroidism type-Ia (PHP-Ia), characterized by renal proximal tubular resistance to parathyroid hormone (PTH), results from maternal mutations of GNAS that lead to loss of α-subunit of the stimulatory G protein (Gαs) activity. Gαs expression is paternally silenced in the renal proximal tubule, and this genomic event is critical for the development of PTH resistance, as patients display impaired hormone action only if the mutation is inherited maternally. The primary clinical finding of PHP-Ia is hypocalcemia, which can lead to various neuromuscular defects including seizures. PHP-Ia patients frequently do not present with hypocalcemia until after infancy, but it has remained uncertain whether PTH resistance occurs in a delayed fashion. Analyzing reported cases of PHP-Ia with documented GNAS mutations and mice heterozygous for disruption of Gnas, we herein determined that the manifestation of PTH resistance caused by the maternal loss of Gαs, ie, hypocalcemia and elevated serum PTH, occurs after early postnatal life. To investigate whether this delay could reflect gradual development of paternal Gαs silencing, we then analyzed renal proximal tubules isolated by laser capture microdissection from mice with either maternal or paternal disruption of Gnas. Our results revealed that, whereas expression of Gαs mRNA in this tissue is predominantly from the maternal Gnas allele at weaning (3 weeks postnatal) and in adulthood, the contributions of the maternal and paternal Gnas alleles to Gαs mRNA expression are equal at postnatal day 3. In contrast, we found that paternal Gαs expression is already markedly repressed in brown adipose tissue at birth. Thus, the mechanisms silencing the paternal Gαs allele in renal proximal tubules are not operational during early postnatal development, and this finding correlates well with the latency of PTH resistance in patients with PHP-Ia.

Pseudohypoparathyroidism with diabetes mellitus and hypothyroidism

We report a 12-year-old child with pseudohypoparathyroidism (PHP) whose mother had pseudopseudohypoparathyroidism. The child had low serum calcium, high phosphorous and high parathormone (PTH) levels. PHP occurs due to a defect in the guanine nucleotide binding protein (G protein). She also had hypothyroidism which is known to utilize the G protein pathway. She developed T 1 diabetes mellitus (T1DM) while under follow-up. This is arguably the first time T1DM has been reported associated with PHP.