what causes the fatty substance on myelin
In certain inherited diseases, the myelin sheath does not develop properly, or it becomes damaged with time. One of the best-known of these disorders is X-linked adrenoleukodystrophy, or X-ALD, which more severely affects males. In X-ALD, an abnormal fatty substance accumulates in the brain, causing damage to the myelin sheath. Symptoms include progressive loss of thinking skills, muscle weakness and seizures. The disease also affects the adrenal gland, which regulates blood pressure and the body's ability to respond appropriately to stress.