This article is written in memory of Sam Tobias, who passed away on Friday, April 5 from ALD. He was 8 years old.
Definition and Symptoms of ALD
Adrenoleukodystrophy or ALD is a genetic neurological disorder that affects 1 in every 17,900 boys worldwide. It is also known as X-ALD since the defect is transmitted through the X chromosome.
Women are carriers of the disease. Boys are affected because they only have one X chromosome. The second X chromosome in girls protects them against the disease. (1)
Childhood-onset ALD is the most severe of the three forms, with symptoms appearing between 4 and 10 years of age. (2)
The other two kinds of ALD are adult-onset ALD (adrenomyeloneuropathy or AMN) which appears between the ages of 21 and 35, and neonatal ALD. Neonatal ALD is not genetically inherited and can affect girls and boys. (3)
Symptoms for AMN may include progressive stiffness, weakness, loss of coordination or paralysis of the lower limbs and extremities. (1)
Adult-onset ALD progresses more slowly than the classic childhood form. “Almost half the women who are carriers of X-ALD will develop a milder form of AMN but almost never develop symptoms seen in boys [with] X-ALD.” (1)
Symptoms of childhood-onset ALD include (1, 4):
• behavioral changes - abnormal withdrawal or aggressive outbursts, poor memory, poor school performance
• visual loss
• learning disabilities
• poorly articulated speech
• difficulty swallowing
• disturbances of gait and coordination
• intermittent vomiting
• increased skin pigmentation
• progressive dementia (1)
These changes occur due to the breakdown of myelin in the brain. The process is called demyelination. Myelin is crucial to the effective transmission of signals between the nerves.
While the exact relationship between ALD and myelin is still being studied, researchers believe that the buildup of saturated, very long-chain fatty acids (VLCFA) in people with X-ALD provokes an immune response from the body which destroys myelin.