Gene: GCM2 – glial cells missing 2
Protein: Chorion-specific transcription factor GCMb
Clinical characteristics:
- Hypocalcemia
- Hyperphosphatemia
- Hypoparathyroidism
- Absence of syndromic features
- Symptoms of acute hypocalcemia:
- Seizures or muscle spasms
- Tingling of lips, tongue, fingers, and toes
- Symptoms of chronic hypocalcemia:
- 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
Inheritance pattern:
- Autosomal recessive
- Autosomal dominant (reported in 2 families)
What this test can tell us:
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 one or two 4-cc tubes of blood in EDTA/ purple top tube (minimum of 1-2 cc for infants).