Neuroimaging of a New Familial Disorder; Ataxia, Chorea, Seizures, and Dementia

The neuropathology of CAG repeat diseases: review and update of genetic and molecular features

Classification of inherited neurodegenerative diseases is increasingly based on their genetic features, which supplement, clarify, and sometimes replace the older clinical and pathologic schemata. This change has been particularly rapid and impressive for the CAG repeat disorders. In Huntington's disease, X-linked spinobulbar muscular atrophy, dentatorubropallidoluysian atrophy, and a series of autosomal dominant cerebellar atrophies, genetic advances have resolved many nosologic issues, and opened new avenues for exploration of pathogenesis. In this review, we summarize classic and current concepts in neuropathology of these CAG repeat diseases.

Dentatorubral and pallidoluysian atrophy (DRPLA). Clinical and neuropathological findings in genetically confirmed North American and European pedigrees

Dentatorubral and pallidoluysian atrophy (DRPLA) is an autosomal dominant disorder that clinically overlaps with Huntington's disease (HD) and manifests combinations of chorea, myoclonus, seizures, ataxia, and dementia. DRPLA is caused by a CAG triplet repeat (CTG-B37) expansion coding for polyglutamine on chromosome 12 and exhibits the genetic phenomenon of anticipation. This neurodegenerative disease has only rarely been reported in non-Japanese pedigrees, and there are only a few neuropathological studies in genetically confirmed patients. We report 10 cases of DRPLA from two North American and two British pedigrees in which CTG-B37 expansions have been demonstrated within each kindred (54-83 repeats), individually in 8 of the 10 cases, and describe the neuropathological findings in 4 cases. Members of DRPLA kindreds have a wide range of clinical phenotypes and markedly variable ages at onset. The neuropathological spectrum is centered around the cerebellifugal and pallidofugal systems, but neurodegenerative changes can be found in many nuclei, tracts, and systems. Evidence of CTG-B37 triplet repeat expansion should be sought in HD-like cases that are negative for expanded triplet repeats within the HD IT15 gene or in autopsy cases with degeneration of the dentatorubral or pallidoluysian systems.

Molecular and clinical findings in a family with dentatorubral-pallidoluysian atrophy

Herein we describe the molecular and clinical findings in a North American Caucasian family with dentatorubral-pallidoluysian atrophy (DRPLA). These patients all presented with an autosomal dominant neurodegenerative disorder characterized by a variable combination of clinical symptoms including seizures, ataxia, dementia, choreiform movements, mental retardation, and psychiatric disease. Neuroradiologic findings in the index case revealed deep subcortical white matter changes on magnetic resonance imaging. Prior to referral, the family carried a diagnosis of Huntington's disease (HD). Subsequent direct molecular testing for HD failed to identify the HD expansion mutation in affected individuals. Molecular testing for DRPLA, however, demonstrated the presence of the recently characterized DRPLA expansion mutation in all affected individuals. The size of the expansion correlated with the age of onset of clinical symptoms. As DRPLA has rarely been reported in North American and European populations, the molecular confirmation of DRPLA in this family provides support for the hypothesis that DRPLA may not be as geographically restricted as once thought.

The Haw River syndrome: dentatorubropallidoluysian atrophy (DRPLA) in an African-American family

Haw River Syndrome (HRS) is a dominant neurodegenerative disease that has affected five generations of an African-American family in rural North Carolina. The disorder represents a unique spectrum of multiple system degenerations resembling Huntington's disease, spinocerebellar atrophy and dentatorubropallidoluysian atrophy (DRPLA), a neurodegenerative disease that has been primarily reported in Japan. Recently, DRPLA has been shown to be due to an expanded trinucleotide repeat located on chromosome 12pter-p12. We have genotyped this family and found HRS to be tightly linked to the DRPLA region. Further examination demonstrates that, despite their distinct cultural origins and clinical and pathological differences, HRS is caused by the same expanded CTG-B37 repeat as DRPLA.