X-linked adrenoleukodystrophy, also called X-ALD, is a degenerative genetic disease. People who suffer from it undergo progressive deterioration of the nervous system and endocrine glands. There are three types with different symptoms and age of appearance, all united by the gradual destruction of myelin.
X-ALD is caused by a mutation in the ABCD1 gene, which is found on the X chromosome. The gene codes for the ALDP protein, which is used to eliminate long and very long-chain saturated fatty acids. When the protein levels are too low, the acids build up and damage the glial cells.
The process is still unclear today, but the results are evident: the cells no longer produce myelin, leaving the nerves uncovered. This causes an immune response, resulting in demyelination. The process therefore feeds itself and is impossible to stop, at least with the tools available.
Symptoms vary by variant type and result in three versions of the disease.
- X-linked brain adrenoleukodystrophy (X-CALD), the most common and severe form. It occurs between 3 and 12 years with reduced adrenal activity, learning difficulties, convulsions. The disease leads to the neurovegetative state in the terminal phase.
- Adrenomyeloneuropathy (AMN), form with adult onset. Between 20 and 30 years, limb stiffness, hand pain, weakness occur. Again, it flows into the vegetative state.
- Adrenoleukodystrophy with isolated adrenal cortic insufficiency (AI), affecting 70% of males with X-ALD. In 10% of cases, the only symptom remains. In others, it is the debut sign for the disease.
The diagnosis of the disease takes place starting from clinical observation, followed by an examination of VLCFA levels and magnetic resonance imaging. The genetic test for the ABCD1 gene confirms the diagnosis and also acts as an antenatal diagnosis.