Adrenoleukodystrophy (ALD) is a rare progressive brain disorder. It is caused by mutations in the ABCD1 gene that lead to an accumulation of saturated very long-chain fatty acids (VLCFAs), and therefore to the destruction of myelin (a protective sheath that insulates nerve fibers).
Recently implemented newborn screening revealed that ALD affects 1:15,500 males, which is higher than previously thought.
What is newborn screening?
Newborn screening is a procedure that enables the identification of genetic disorders before symptoms appear. It is used for diseases where early diagnosis has a direct positive impact on the health of the newborn.
A newborn screening test for ALD includes biochemical analysis of VLCFA levels in the blood. Blood is taken from the newborn’s heel, and is also used to screen for other conditions. Elevated VLCFA levels are an indication for ALD but are not specific to the disease. For this reason, a genetic test that identifies the presence of mutations in the ABCD1 gene is required for a final diagnosis if high levels of VLCFA are detected in the blood.
Several U. S. states recently included ALD into their routine newborn screening programs. More states plan to follow.
Why is newborn screening for ALD important?
Current ALD treatments can only inhibit the progression of the disease, but they cannot reverse it. Therefore, early detection and treatment are essential.
Stem cell therapy is the standard of care for childhood cerebral ALD (CALD). Because stem cell transplantation is risky, it is not started before the first signs of the disease appear. It is the most effective in the early stages of CALD, so there is a narrow therapeutic window for this procedure.
ALD is asymptomatic at birth, and it is not possible to predict whether a child will develop the more severe form of the disease, CALD, or adrenomyeloneuropathy (AMN) during adulthood. A child with a known predisposition for ALD will be examined regularly for neurological signs of the condition. This is done by magnetic resonance imaging (MRI), which should be performed at six-month intervals.
The child will also be monitored for signs of adrenal insufficiency which causes Addison’s disease. Addison’s disease — when adrenal glands do not produce sufficient amounts of steroid hormones — can be efficiently treated with corticosteroid replacement therapy. Knowing that the child has a predisposition for ALD will also facilitate the diagnosis for Addison’s disease once symptoms appear.
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