Neonatal Severe Hyperparathyreoidismus(NSHPT)

Summary:
NSHPT is a rare, life-threatening genetic disorder in newborns caused by excessive parathyroid hormone (PTH) production. This results in severe hypercalcemia and potential fatal complications. Diagnosis involves clinical evaluation and genetic testing. Treatment includes medications and, often, surgical removal of the parathyroid glands.

Causes and Mechanism

  • Genetics: NSHPT is caused by homozygous or compound heterozygous mutations in the CASR gene, leading to complete loss of receptor function.
  • Mechanism: The impaired calcium-sensing receptor in the parathyroid glands and kidneys fails to regulate calcium levels, resulting in extreme overproduction of PTH and severe hypercalcemia.

In contrast to FHH, where a single CASR mutation leads to a mild condition, NSHPT arises from mutations in both copies of the gene, causing a more severe and early-onset disease.

Symptoms

Symptoms often appear shortly after birth and include:

  • Severe Hypercalcemia
  • Muscle Weakness and Hypotonia
  • Feeding difficulties
  • Vomiting
  • Poor growth (failure to thrive)
  • Bone damage due to excessive bone resorption (osteopenia or osteoporosis)
  • Respiratory distress due to muscle weakness

Untreated NSHPT can lead to:

  • Kidney failure
  • Respiratory failure
  • Heart rhythm disturbances

Diagnosis

  1. Blood Tests:
    • Elevated calcium levels significantly higher than in FHH.
    • Markedly elevated PTH levels.
  2. Genetic Testing:
    • Confirmation of homozygous or compound heterozygous mutations in the CASR gene.

Treatment

NSHPT requires urgent and aggressive intervention:

  1. Medications:
    • Calcium-binding agents and calcitonin to rapidly lower calcium levels.
  2. Hydration and Diuretics:
    • Intravenous fluids and diuretics (e.g., furosemide) to promote calcium excretion.
  3. Surgical Therapy:
    • Subtotal or total parathyroidectomy is usually necessary to stop excessive PTH production.
    • Post-surgery, patients often require lifelong calcium and vitamin D supplementation to compensate for the loss of parathyroid function.

Prognosis

  • With Treatment: Early diagnosis and treatment significantly improve outcomes, and patients can achieve good long-term health with proper management.
  • Without Treatment: The condition is almost always fatal.

Long-term follow-up is essential to monitor calcium levels and prevent complications.