Test and teach. Number seventy-three. Diagnosis: Alexander's disease.

Alexander's disease is a progressive degenerative neurological disorder developing in early childhood which is characterized by accumulation of Rosenthal fibres throughout the cerebral white matter. These fibres are composed of glial fibrillary acidic protein and ubiquinated alpha beta crystallin. The absence of atypia, increased cellularity, mitotic activity or necrosis in biopsy material allows differentiation from neoplasia glial processes. Clinical features suggestive of the diagnosis include progressive mental retardation with an increase in head circumference.