Hypomyelination and congenital cataract

Alternate names

Leukodystrophy, hypomyelinating, 5; HLD5; Hypomyelination - congenital cataract

Definition

Hypomyelination and congenital cataract is a very rare disease characterized by cloudy coverings of the eye that are present at birth (congenital cataracts) and neurologic impairment that becomes apparent after the first year of life.

Cause

• Hypomyelination and congenital cataract is caused by a change (mutation ) in the FAM126A gene.
• The FAM126A gene provides instructions for making a protein called hyccin, the function of which is not completely understood.
• Hyccin is involved in the formation of myelin throughout the nervous system.

Gene mutations

• Most FAM126A gene mutations that cause hypomyelination and congenital cataract prevent the production of hyccin.
• People who cannot produce any hyccin have problems forming myelin, leading to the signs and symptoms of this condition.

Inheritance

Autosomal recessive inheritance, a 25% chance

It is inherited in an autosomal recessive manner.

Signs and symptoms

• This condition is characterized by cloudy coverings of the eye that are present at birth (congenital cataracts) and neurologic impairment that becomes apparent after the first year of life.
• The neurologic impairment is progressive and presents as ataxia and spasticity.
• Affected individuals may lose the ability to walk.
• Signs and symptoms may vary but can include loss of sensation in the hands and feet (peripheral neuropathy), curvature of the spine (scoliosis), difficulty speaking (dysarthria), seizures, and moderate intellectual disability.

Clinical presentation

For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed.

80%-99% of people have these symptoms

• Abnormal cerebellum morphology(Abnormality of the cerebellum)
• Abnormal pyramidal sign
• Cerebral hypomyelination
• Developmental cataract(Clouding of the lens of the eye at birth)
• Global developmental delay
• Intellectual disability, moderate(IQ between 34 and 49)

Diagnosis

• Diagnosis of hypomyelination and congenital cataract is based on clinical findings of muscle weakness and cataracts, and a brain MRI that indicates a loss of the myelin surrounding the neurons.
• The diagnosis can be confirmed by genetic testing of the FAM126A gene.

Treatment

• Treatment is focused on relieving symptoms of the condition and may include physical therapy, special education, and medication to treat seizures.
• Cataract extraction usually in the first months of life.
• Therapy support for developmental delays
• Special education
• Physical medicine and rehabilitation for spasticity and ataxia.
• Treatment for scoliosis and contractures per orthopedist
• Feeding therapy and or gastrostomy tube as needed.<ref>Wolf NI, Biancheri R, Zara F, et al. Hypomyelination and Congenital Cataract. 2008 Oct 14 [Updated 2021 Jan 14]. In: Adam MP, Ardinger HH, Pagon RA, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2021. Available from: https://www.ncbi.nlm.nih.gov/books/NBK2587/</ref>[1].

References

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NIH genetic and rare disease info

• NIH info on Hypomyelination and congenital cataract

Hypomyelination and congenital cataract is a rare disease.

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