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Alexander Disease is an extremely rare, progressive, neurological disorder that usually becomes apparent during infancy
or early childhood. However, less commonly, cases have been described in which symptom onset has occurred in later childhood
or adolescence (juvenile onset) or, rarely, during the third to fifth decades of life (adult onset). Alexander Disease belongs
to a group of rare disorders known as leukodystrophies, which are characterized by degenerative changes of the white matter
of the brain. More specifically, in Alexander Disease there is a lack of normal amounts of the protective, fatty material
(myelin) that forms an insulating wrapping (sheath) around certain nerve fibers (axons). Myelin enables the efficient transmission
of nerve impulses and provides the "whitish" appearance of the so-called white matter of the brain. Alexander Disease
is characterized by deficient myelin formation in infants, and sometimes in juvenile cases, that is most prominent in the
front (i.e., frontal) lobes of the brain's two hemispheres (cerebrum). The disorder is also associated with the formation
of abnormal, fibrous deposits known as "Rosenthal fibers" throughout certain regions of the brain and spinal cord
(central nervous system [CNS]).
In infants and young children affected by Alexander Disease, associated symptoms and findings include a failure to grow
and gain weight at the expected rate (failure to thrive); delays in the development of certain physical, mental, and behavioral
skills that are typically acquired at particular stages (psychomotor retardation); and progressive enlargement of the head
(macrocephaly). Additional features typically include sudden episodes of uncontrolled electrical activity in the brain (seizures);
abnormally increased muscle stiffness and restriction of movement (spasticity); and progressive neurological deterioration.
In some cases, there is hydrocephalus. In most cases, Alexander Disease appears to occur randomly for unknown reasons (sporadically),
with no family history of the disease. In an extremely small number of cases, it is thought that the disorder may have affected
more than one family member.
Contributed from - www.rarediseases.org
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