Hypomyelination-congenital cataract syndrome
Medical condition
From Wikipedia, the free encyclopedia
Hypomyelination-congenital cataract syndrome is a rare autosomal recessive hereditary disorder that affects the brain's white matter[1] and is characterized by congenital cataract (or cataracts that begin in the first two months of life), psychomotor development delays, and moderate intellectual disabilities. It is a type of leukoencephalopathy.[2]
| Hypomyelination-congenital cataract syndrome | |
|---|---|
| Other names | HCC |
| |
| Specialty | Medical genetics |
| Prevention | None |
| Prognosis | Medium |
| Frequency | rare, only 24 cases have been described in medical literature |
| Deaths | - |
Signs and symptoms
Children with this condition are born with congenital cataract (or they have an early-onset cataract which presents before two months of life). These cataracts are caused by hypomyelination, which is the body's inability of producing nerve fiber myelin.[3] Development is normal for kids with this condition until the age of 1 year of life, when development and learning start slowing down, although they can learn how to walk.[3]
Other symptoms such as intellectual disabilities, cognitive impairment, epilepsy, ataxia, spasticity, trunk hypotonia, hyperreflexia, tremors, and difficulties with speech are also seen in patients.[3][4][5][6]
Complications
Due to the hypomyelination mentioned beforehand, individuals with this condition start losing sensation in their arms and legs, something which is known medically as peripheral neuropathy.[3]Although walking can be achieved by the age of 1, it can be impaired later in life due to a progressive scoliosis and muscle weakness with accompanying muscle atrophy which are often seen in patients with the condition.[3]
Congenital cataract results in visual impairment.[3]
Genetics
This condition is caused by autosomal recessive mutations in the FAM126A gene, located in chromosome 7. These mutations can either be deletions, loss-of-function, or be caused by amino acid substitutions.[7][8] These mutations prevent FAM126 from making hyccin, this absence of hyccin is what causes the impaired ability of producing myelin in individuals with this condition.[7][8]
Other mutations involved in hypomyelination-congenital cataract syndrome actually allow the production of a reasonable amount of hyccin, individuals with this kind of mutations don't experience peripheral neuropathy and they keep the ability of walking for a longer period of time than those who have the more common loss-of-function FAM126A mutations.[7]
Management
The walking impairments can be managed with physical support.[citation needed]
The congenital catact can be managed with intraocular lens corrective surgery, after this surgery, contact lenses can be used for the child to be able to see correctly.[9]