A novel case of neonatal severe hyperparathyroidism successfully treated with a type II calcimimetic drug

Neonatal Severe Hyperparathyroidism Causing Life-Threatening Hypercalcemia Treated With Medical and Surgical Management

A 3-day-old male presented to a peripheral remote hospital in New South Wales, Australia, with tachypnea. He was found to have hypercalcemia, with ionized calcium >2.5 mmol/L (>10 mg/dL) (0.97-1.5 mmol/L or 1.14-1.3 mg/dL) and serum calcium of 3.85 mmol/L (15.43 mg/dL) (2.2-2.8 mmol/L or 8.5-10.5 mg/dL). Peak serum calcium was 5.4 mmol/L (21.64 mg/dL). He was transferred to a tertiary pediatric intensive care unit. Medical management (including hyperhydration, diuretics, corticosteroids, bisphosphonates, cinacalcet, and calcitonin) failed to maintain normocalcemia; therefore, total parathyroidectomy was performed on day 16 of life. Hungry bones syndrome developed postoperatively, requiring high doses of calcium, calcitriol, and phosphate supplementation. Genetic testing identified compound heterozygosity for 2 likely pathogenic variants in the calcium-sensing receptor gene. He is now 3 years old and is growing and developing without any concerns. This case highlights the importance of aggressive initial management in addressing severe hypercalcemia through perioperative management principles as well as the prolonged nature of hungry bones syndrome.

Genetics of hereditary forms of primary hyperparathyroidism

Primary hyperparathyroidism (PHPT), a relatively common disorder characterized by hypercalcemia with raised or inappropriately normal serum parathyroid hormone (PTH) concentrations, may occur as part of a hereditary syndromic disorder or as a non-syndromic disease. The associated syndromic disorders include multiple endocrine neoplasia types 1-5 (MEN1-5) and hyperparathyroidism with jaw tumor (HPT-JT) syndromes, and the non-syndromic forms include familial hypocalciuric hypercalcemia types 1-3 (FHH1-3), familial isolated hyperparathyroidism (FIHP), and neonatal severe hyperparathyroidism (NS-HPT). Such hereditary forms may occur in > 10% of patients with PHPT, and their recognition is important for implementation of gene-specific screening protocols and investigations for other associated tumors. Syndromic PHPT tends to be multifocal and multiglandular with most patients requiring parathyroidectomy with the aim of limiting end-organ damage associated with hypercalcemia, particularly osteoporosis, nephrolithiasis, and renal failure. Some patients with non-syndromic PHPT may have mutations of the MEN1 gene or the calcium-sensing receptor (CASR), whose loss of function mutations usually cause FHH1, a disorder associated with mild hypercalcemia and may follow a benign clinical course. Measurement of the urinary calcium-to-creatinine ratio clearance (UCCR) may help to distinguish patients with FHH from those with PHPT, as the majority of FHH patients have low urinary calcium excretion (UCCR < 0.01). Once genetic testing confirms a hereditary cause of PHPT, further genetic testing can be offered to the patients' relatives and subsequent screening can be carried out in these affected family members, which prevents inappropriate testing in normal individuals.

Expert consensus on multidisciplinary approach to the diagnosis and treatment of primary hyperparathyroidism in pregnancy in China

Primary hyperparathyroidism in pregnancy is a rare disease that can have detrimental effects on both maternal and fetal/neonatal outcomes. The physiological changes that occur during pregnancy can complicate the diagnosis, imaging examinations, and treatment of this disorder. To enhance our understanding and management of primary hyperparathyroidism in pregnancy, experts from various fields, including endocrinology, obstetrics, surgery, ultrasonography, nuclear medicine, pediatrics, nephrology, and general practice in China, collaborated to develop a consensus addressing the critical aspects of the diagnosis and treatment of primary hyperparathyroidism in pregnancy with a multidisciplinary team approach. This consensus provides valuable guidance for healthcare professionals in managing this condition, ultimately improving outcomes for both mothers and their babies.

Subtotal Parathyroidectomy Successfully Controls Calcium Levels of Patients with Neonatal Severe Hyperparathyroidism Carrying a Novel CASR Mutation

INTRODUCTION

Inactivating mutations of the calcium-sensing receptor (CASR) gene result in neonatal severe hyperparathyroidism (NSHPT). Total parathyroidectomy is an effective way to control life-threatening hypercalcemia in NSHPT but leads to permanent hypoparathyroidism. An alternative surgical option is subtotal parathyroidectomy. However, few cases were reported in the literature. Here, we report two unrelated NSHPT patients, one with a novel homozygous mutation (c.1817T>C; p.Leu606Pro) in CASRand the other with heterozygous for the same mutation who also carried two rare intronic variants in CASR. The outcomes of subtotal parathyroidectomy in these patients are also described.

CASE PRESENTATION

Two infants presented with an alteration of consciousness, respiratory distress, and bradycardia. Severe hypercalcemia, hypophosphatemia, and markedly elevated parathyroid hormone levels were identified, suggesting NSHPT. Cinacalcet was unable to control calcium (Ca) levels of both patients. A novel heterozygous and homozygous missense mutation c.1817T>C; p.Leu606Pro was identified in patients 1 and 2, respectively. Based on the model prediction, proline substitution at Leu606 is likely to disrupt conversion between the active and inactive conformations at the extracellular to transmembrane domain interface of CASR. In addition, two extremely rare intronic variants in CASR (chr3:g.122180314A>G and chr3:g.122251601G>A, based on GRCh38) were identified in patient 1 and his mother. These variants might have contributed to the clinical manifestations of patient 1 who was heterozygous for the c.1817T>C; p.Leu606Pro variant. Subtotal parathyroidectomy was performed by removing three and a half parathyroid glands. So far, patient 1 has been in normocalcemia for 5 years. Patient 2 was in normocalcemia for 16 months after surgery and subsequently developed mild hypoparathyroidism which required only low-dose calcitriol treatment.

CONCLUSION

We report a novel heterozygous and homozygous missense variant (c.1817T>C; p.Leu606Pro) in CASR in two NSHPT patients. The mutation likely disrupts conformational changes of CASR and results in cinacalcet unresponsiveness. Intronic variants in CASR identified in the patient with heterozygous variant might have contributed to the clinical manifestations of the patient. Although total parathyroidectomy is widely accepted as a standard treatment for NSHPT, we demonstrate that subtotal parathyroidectomy is also an effective procedure to normalize Ca levels and allow these patients to be in normocalcemia or mild hypoparathyroidism, which is simply controlled by low-dose calcitriol treatment. Subtotal parathyroidectomy appeared to be an effective treatment for NSHPT regardless of the molecular etiologies.

A Case of Neonatal Severe Hyperparathyroidism: Challenges in Management

Neonatal severe hyperparathyroidism is a rare disorder arising from inherited defects in the calcium sensing receptor (CaSR) that presents early in life with severe hypercalcemia, failure to thrive, and developmental retardation. The authors describe an infant with neonatal severe hyperparathyroidism due to homozygous CaSR gene mutation presenting with recurrent episodes of severe hypercalcemia, growth retardation, and developmental delay. Medical management served as an effective bridge therapy to surgery. Total parathyroidectomy with right hemithyroidectomy was performed at 7 mo of age and resulted in successful cure and normalization of growth and developmental milestones. Timely medical and surgical management can help prevent mortality and morbidity in the form of neurodevelopmental sequelae. Life-long monitoring and treatment is mandatory for the resultant hypoparathyroidism.

Successful use of cinacalcet monotherapy in the management of siblings with homozygous calcium-sensing receptor mutation

OBJECTIVES

Neonatal severe hyperparathyroidism (NSHPT) due to pathogenic mutations in the calcium-sensing receptor (CASR) is a serious medical condition that can lead to symptomatic hypercalcaemia and has detrimental effects on a child's growth and development. What is new: This report adds to evidence that homozygous CASR mutations can be managed with cinacalcet monotherapy as an alternative to parathyroidectomy. And, early use of cinacalcet in NSHPT can result in improvements in symptoms, growth and developmental milestones.

CASE PRESENTATION

We present two siblings with NSHPT due to homozygous mutation in the CASR gene with moderate hypercalcaemia. Both were treated with cinacalcet monotherapy and showed significant improvement in growth parameters including head circumference, developmental milestones and hypercalcaemic symptoms, once their calcium and parathyroid hormone levels normalised.

CONCLUSIONS

This report highlights the role of cinacalcet in managing elevated serum calcium levels in a select group of infants with NSHPT due to homozygous CASR mutations, resulting in improvement in hypercalcaemic symptoms, growth and neurodevelopmental outcomes.

Off-label use of cinacalcet in pediatric primary hyperparathyroidism: A French multicenter experience

BACKGROUND

Cinacalcet is a calcimimetic approved in adults with primary hyperparathyroidism (PHPT). Few cases reports described its use in pediatric HPT, with challenges related to the risk of hypocalcemia, increased QT interval and drug interactions. In this study, we report the French experience in this setting.

METHODS

We retrospectively analyzed data from 18 pediatric patients from 7 tertiary centers who received cinacalcet for PHPT. The results are presented as median (interquartile range).

RESULTS

At a median age of 10.8 (2.0-14.4) years, 18 patients received cinacalcet for primary HPT (N = 13 inactive CASR mutation, N = 1 CDC73 mutation, N = 1 multiple endocrine neoplasia type 1, N=3 unknown etiology). Cinacalcet was introduced at an estimated glomerular filtration rate (eGFR) of 120 (111-130) mL/min/1.73 m², plasma calcium of 3.04 (2.96-3.14) mmol/L, plasma phosphate of 1.1 (1.0-1.3) mmol/L, age-standardized (z score) phosphate of -3.0 (-3.5;-1.9), total ALP of 212 (164-245) UI/L, 25-OHD of 37 (20-46) ng/L, age-standardized (z score) ALP of -2.4 (-3.7;-1.4), PTH of 75 (59-123) ng/L corresponding to 1.2 (1.0-2.3)-time the upper limit for normal (ULN). The starting daily dose of cinacalcet was 0.7 (0.6-1.0) mg/kg, with a maximum dose of 1.0 (0.9-1.4) mg/kg per day. With a follow-up of 2.2 (1.3-4.3) years on cinacalcet therapy, PTH and calcium significantly decreased to 37 (34-54) ng/L, corresponding to 0.8 (0.5-0.8) ULN (p = 0.01), and 2.66 (2.55-2.90) mmol/L (p = 0.002), respectively. In contrast, eGFR, 25-OHD, ALP and phosphate and urinary calcium levels remained stable. Nephrocalcinosis was not reported but one patient displayed nephrolithiasis. Cinacalcet was progressively withdrawn in three patients; no side effects were reported.

CONCLUSIONS

Cinacalcet in pediatric HPT can control hypercalcemia and PTH without significant side effects.