Hypomyelination and Congenital Cataract

Also known as: hypomyelinating leukodystrophy 5 (HLD5)

Gene: FAM126A (also known as DRCTNNB1A)

Protein: hyccin

Clinical Characteristics

  • Bilateral congenital cataracts
  • Normal psychomotor development in first year of life
  • Progressive ataxia and spasticity
  • Mild to moderate cognitive impairment
  • Hypotonia
  • Dysarthria
  • Truncal titubation and intention tremor
  • Peripheral neuropathy
  • Progressive scoliosis
  • Characteristic MRI findings:
    • Diffusely abnormal supratentorial white matter
    • Sparing of the cortical and deep gray matter structures
    • Hypomyelination of supratentorial white matter +/- deep cerebellar white matter
    • Increased white matter water content
    • White matter bulk loss and gliosis in older individuals

Inheritance pattern: Autosomal recessive

What Can Be Learned From This Test

Testing is performed by sequencing the entire coding region and intron-exon junctions of FAM126A. This assay will detect point mutations, small deletions and small insertions. It will not detect a partial or whole gene deletion or duplication.

A negative test does not rule out a genetic cause of a neurologic disorder. There are many other genes associated with different types of neurologic disorders and leukodystrophies, some of which are available for testing in our laboratory and can be performed if clinically indicated. 

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: $1,180

Known Variant Testing

  • Code: 81479
  • Cost: $225

Additional Information