Infantile Reflux Disease (IRD)
- National Institute of Health
Infantile Refsum Disease (IRD) is a medical condition within the Zellweger spectrum of perixisome biogenesis disorders (PBDs), inherited genetic disorders that damage the brain's white matter and affect motor movements. PBDs are part of a wider group of conditions called leukodystrophies. The Zellweger spectrum of PBDs includes related, but not more serious, conditions referred to as Zellweger syndrome (ZS) and neonatal adrenoleukodystrophy. Collectively, these conditions are caused by hereditary defects in one of the 12 genes, called PEX genes, that are necessary for the normal formation and function of peroxisomes. Peroxisomes are cell structures necessary for the normal formation and function of the brain, eyes, liver, kidneys and bones. They contain enzymes that break down toxins in cells, including very long chain fatty acids and phytic acid (a type of fat found in certain foods), and synthesize certain fats (lipids) that are necessary for cell function. When peroxisomes fail to function, there is an over-accumulation of very long chain fatty acids and phytanic acid, and a lack of bile acids and plasmalogens - specialized lipids found in cell membranes and enveloping and protecting the myelin sheaths and nerve fibers. has some residual perixisome function resulting in less severe disease than Zellweger syndrome. Symptoms of IRD begin in childhood with retinitis pigmentosa, a visual impairment that often leads to blindness, and hearing problems that usually progress to deafness in early childhood. Other symptoms may include rapid, jerky eye movements (nystagmus); weak muscle tone (hypotonia) and lack of muscle coordination (ataxia); mental and growth disorders; abnormal facial features; enlarged liver; and abnormalities in brain myelin white matter. At the mildest extreme of the condition, intellect can be preserved. Although adult Refsum and IRD disease have similar names, they are separate conditions caused by different gene defects.
The primary treatment for IRD is to avoid foods containing phytic acid, including dairy products; beef and lamb; and fatty fish such as tuna, cod and haddock. While this prevents the accumulation of phytic acid, it does not involve the accumulation of very long chain fatty acids and the deficiency of bile acids and plasmalogens.
IRD is a deadly disease, but some children will survive into their teens and 20s, and possibly beyond.
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