Alexander disease is a very rare autosomal dominant leukodystrophy, which are neurological conditions caused by anomalies in the myelin which protects nerve fibers in the brain.

These children may have excessive vomiting, difficulty swallowing and speaking, poor coordination, and loss of motor control.

According to the National Institute of Neurological Disorders and Stroke, the destruction of white matter is accompanied by the formation of Rosenthal fibers—abnormal clumps of protein that accumulate in astrocytes in the brain.

[1] Delays in development of some physical, psychological and behavioral skills; progressive enlargement of the head (macrocephaly), seizures, spasticity, and in some cases also hydrocephalus, idiopathic intracranial hypertension, and dementia.

In cases of type I Alexander disease, where the condition appears before age 4, symptoms include seizures, enlarged brain and head, stiffness in the limbs, delayed intellectual and physical development, recurrent vomiting, and difficulties with gaining weight.

The destruction of white matter in the brain is accompanied by the formation of fibrous, eosinophilic deposits known as Rosenthal fibers.

[2][7][8] Rosenthal fibers appear not to be present in healthy people,[7][9] but occur in specific diseases, like some forms of cancer, Alzheimer's, Parkinson's, Huntington's, and ALS.

[14][15] A rough diagnosis may also be made through revealing of clinical symptoms, including enlarged head size, along with radiological studies, and negative tests for other leukodystrophies.

[9] No cure or standard procedure for treatment is known, although a University of Wisconsin study shows promise with gene editing of the astrocytes.

[2][7][10] A phase III clinical trial of an antisense therapy, sponsored by Ionis Pharmaceuticals, began in 2021.