Infantile refsum disease

Infantile Refsum disease (IRD) is one of a small group of genetic diseases called peroxisome biogenesis disorders (PBD), which are part of a larger group of diseases called the leukodystrophies.

These are inherited conditions that damage the white matter of the brain and affect motor movements. IRD is the mildest of the PBDs; Zellweger syndrome, neonatal adrenoleukodystrophy, and rhizomelic chondrodysplasia have similar, but more severe symptoms.

Etiology
The PBDs are caused by defects in the genes that are associated with the breakdown of phytanic acid, a substance commonly found in foods. As a result, toxic levels of phytanic acid build up in the brain, blood, and other tissues.

Symptoms
Symptoms of IRD begin in infancy with a visual impairment called retinitis pigmentosa, which often leads to blindness, and hearing problems that usually progress to deafness by early childhood.

Other symptoms may include rapid, jerky eye movements (nystagmus); floppy muscle tone (hypotonia) and lack of muscle coordination (ataxia); mental and growth retardation; mild abnormalities in the form and structure of the face (dysmorphia); enlargement of the liver (hepatomegaly); and low cholesterol (hypocholesterolemia).

Although Adult Refsum disease and IRD have similar names, they are separate disorders caused by different biomechanisms involved in the breakdown of phytanic acid.

Treatment
The primary treatment for IRD is to avoid foods that contain phytanic acid, including dairy products; beef and lamb; and fatty fish such as tuna, cod, and haddock. Some infants and children may also require plasma exchange (plasmapheresis) in which blood is drawn, filtered, and reinfused back into the body, to control the buildup of phytanic acid.

Prognosis
IRD is a fatal disease, but some children will survive into their teens and twenties, and possibly even beyond.