Familial Isolated Hypoparathyroidism

Gene: GCM2 – glial cells missing 2

Protein: chorion-specific transcription factor GCMb

Clinical Characteristics

  • Hypocalcemia
    • Acute hypocalcemia symptoms:
      • Seizures or muscle spasms
      • Tingling of lips, tongue, fingers and toes
  • Chronic hypocalcemia symptoms:
    •  May be asymptomatic
    • Muscle spasms or muscle stiffness
    • Calcium and iron deposits found on CT scan of the brain
    • Abnormal involuntary movements or decrease of voluntary movements
    • Cataracts
    • Coarse brittle hair or hair loss
    • Abnormalities of the teeth
    • Mental retardation
    • Personality disorders
  • Hyperphosphatemia
  • Hypoparathyroidism
  • Absence of syndromic features

Inheritance pattern:

  • Autosomal recessive
  • Autosomal dominant (reported in two families)

What Can Be Learned From This Test

Testing is performed by sequencing the entire coding region of the GCM2 gene. This will detect point mutations, small deletions and small insertions. It will not detect a partial or whole gene deletion or duplication.

A negative test result does not rule out a diagnosis of familial isolated hypoparathyroidism (FIH). Other genes are known to be associated with FIH and this test will only detect mutations in GCM2.

Sample Requirements

Draw 2ml–4ml of blood in EDTA/purple-top tube (minimum of 1ml–2ml for infants).

Turnaround time: 10-14 business days

CPT Codes and Cost

Full Gene Sequencing

  • Code: 81479
  • Cost: $500

Known Variant Testing

  • Code: 81479
  • Cost: $225

Additional Information