A case study from Turkey of a large family, with several members having Friedreich’s ataxia with atypical features, illustrates the genetic complexity of the disease and points to the difficulties of genetic counseling, especially in consanguineous (or inter-related) families.
Friedreich’s ataxia is caused by a three-letter expansion in a gene called frataxin. Upon genetic testing, this expansion was detected in all the family members, who were either affected by the disease or were carriers, except for one who had mental and motor retardation, among other conditions. A number of family members had late-onset symptoms (after 25 years of age) and no cardiac involvement, which is unusual in this disease.
The study, “Atypical Features in a Large Turkish Family Affected with Friedreich Ataxia,” was published in the journal Case Reports in Neurological Medicine.
All members of a family affected by Friedreich’s ataxia should be genotyped before a comprehensive genetic counseling is delivered, suggested the study’s first author, Dr. Semiha Kurt, with the Department of Neurology at Gaziosmanpasa University in Tokat.
The family described comprises four generations and 39 individuals. There were four consanguineous (blood-related) unions in the family, with one in the first generation, one in the second and two in the third.
Four people in the third generation were diagnosed with Friedreich’s ataxia, and tested positive for the three-letter expansion in the frataxin gene. Eight in the fourth generation were carriers of the mutation and one, an 11-year old girl, tested negative for repeat expansion in the frataxin gene. However, she had a number of complications, including mental retardation, motor dysfunction, and epilepsy. Her parents were consanguineous.
The researchers provided a detailed description of the clinical features of several of the members of the family, including neurological, genetic and cardiac analyses. They reported brain lesions, demyelinating neuropathy, but no significant cardiac involvement.
“Description of [Friedreich’s ataxia] families with different ethnic backgrounds may assist in identifying possible phenotypic and genetic features of the disease,” the authors concluded.
Friedreich’s ataxia is a genetic neurodegenerative disorder, and the most common form of hereditary ataxia, or lack of coordinated muscle movements. It affects around 1 in 50,000 individuals worldwide.