It is inherited in an autosomal dominant manner, such that the child of a parent with the disease has a 50% chance of inheriting the condition, if the parent is heterozygotic. However, most cases arise de novo as the result of sporadic mutations.Alexander disease belongs to leukodystrophies, a group of diseases that affect the growth or development of the myelin sheath. The destruction of white matter in the brain is accompanied by the formation of fibrous, eosinophilic deposits known as Rosenthal fibers. Rosenthal fibers appear not to be present in healthy people, but occur in specific diseases, like some forms of cancer, Alzheimer’s, Parkinson’s, Huntington’s, and ALS. The Rosenthal fibers found in Alexander disease do not share the distribution or concentration of other diseases and disorders. Pathology
Alexander disease causes the gradual loss of bodily functions and the ability to talk. It also causes an overload of long-chain fatty acids in the brain, which destroy the myelin sheath. The cause of Alexander disease is a mutation in the gene encoding GFAP.A CT scan shows:

Decreased density of white matter
Frontal lobe predominance
Dilated lateral ventricles may present

Diagnosis
Detecting the signs of Alexander disease is possible with magnetic resonance imaging (MRI), which looks for specific changes in the brain that may be tell-tale signs for the disease. It is even possible to detect adult-onset Alexander disease with MRI. Alexander disease may also be revealed by genetic testing for its known cause.
Chondrodermatitis nodularis chronica helicis is a small, nodular, tender, chronic inflammatory lesion occurring on the helix of the ear, most often in men. : 610  it often presents as a benign painful erythematous nodule fixed to the cartilage of the helix or antihelix of the external ear. Although the exact cause of the condition is unknown, it has been linked to head pressure on the ear while sleeping. Treatment options include the use of pressure-relieving devices or, in cases where that is not an option, surgery. See also
List of cutaneous conditions


== References ==