Alexander Disease
Alexanders disease is the rarest of the identified leukodystrophies. The infantile form tends to appear between birth and two years, and most sufferers of this form do not survive past the age of 5 or 6. The destruction of the white matter in the brain is accompanied by the formation of fibrous, eosinophilic deposits. These are known as Rosenthal fibres.
Alexanders tends to be sporadic, appearing in families with no known history of the disorder. It is progressive, affects mostly males, and leads to both physical and mental retardation and dementia. The brain and head become progressively larger, leading the increased spasticity and sometimes seizures.
The myelin sheath of both the sensory and motor fibre tracts is affected in Alexander's disease. The Rosenthal fibres are found distributed near the blood vessels of the brain and on the brain's surface. The nerves affected by the disease's demyelination do not correspond with the distribution of the Rosenthal fibres, and these two effects seem to be otherwise unrelated expressions of the disorder.
The exact metabolic error that causes Alexanders disease is unknown, but it is thought to be an autosomal recessive disorder, which may affect both males and females. The demyelination seems to be cause by the destruction of the astrocytic glial cells.
An exact diagnosis of Alexander's disease may not be possible without study of post-mortem tissues or brain or nerve biopsy.
As well as the infantile form of the disease, Alexander's disease is believed to have juvenile and adult onset forms. These occur less frequently and do not progress as rapidly as the infantile form. Older sufferers have widespread formation of Rosenthal fibres throughout their central nervous system, but have less white matter loss and therefore milder symptoms. Whether, however, the disorders described in older children and adults are all actually 'Alexander's disease' or in fact some other similar disorder has not been determined.
Treatment of Alexanders disease is symptomatic and supportive.
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Alexander Disease [external website]