Friedreich’s ataxia can occur as a late-onset disease, with symptoms appearing after age 50, a case-report shows.
Late-onset cases lack the typical symptoms and disease progresses slowly, highlighting the need for genetic testing in cases of older patients showing difficulty coordinating movements or other atypical presentations to confirm the diagnosis.
The study, “Very-late-onset Friedreich’s ataxia: diagnosis in a kindred with late- onset cerebellar ataxia,” was published in the journal Practical Neurology.
The onset of classical Friedreich’s ataxia occurs before age 25, with later onset — between the ages of 25 to 40, or even later (past 40) rarely being reported.
In this study, however, researchers describe the case of a woman with very-late-onset Friedreich’s ataxia. Although rare, late-onset Friedreich’s ataxia occurs in 25% of the cases. Late-onset forms of Friedreichs’s ataxia usually do not show the disease’s typical symptoms, such as cardiac involvement, diabetes mellitus, or scoliosis, which may contribute to a misdiagnosis.
The 58-year-old woman had a seven-year history of slurred speech, along with four years of poor balance and loss of sensory feeling. Clinical examination showed that the patient suffered from weakness in the speech muscles (dysarthria), mild tremor in the arms, lacked body movement coordination (dysmetria), and had reduced vibration sense and ankle reflex.
Nerve conduction tests showed damage to large nerves; a brain scan showed a mild brain shrinkage (atrophy).
A family history analysis revealed that the woman had a sister, age 57, with poor balance issues for the past two to three years, which prompted clinicians to perform a genetic test.
The analysis showed that both sisters had an expansion in the GAA trinucleotide repeat in the FXN gene — the underlying cause of Friedreich’s ataxia — in both alleles (the two versions of a gene). One allele had 80 to 100 repeats, and another more than 800.
Since the genetic findings supported a family history, clinicians also tested their brother, aged 50, who had began reporting very subtle balance difficulties.
Clinical examination showed that he, too, had mild dysarthria and a reduction in vibration sense. Although his walking was only slightly impaired, genetic testing showed he also carried repeats in the FXN gene. Unlike the older sister, both younger siblings showed no evident signs of brain shrinkage.
None of the family members presented Friedreich’s ataxia classical symptoms of heart condition, deafness, scoliosis, pes cavus (high foot arch), or diabetes mellitus.
Since the smaller of the two expansions is the major determinant of disease manifestation, the repeat of just 80–100 repeats (less than 300 repeats) might explain the very-late-onset of the disease and its mild presentation.
Overall, this case-report supports the need for clinicians to consider “genetic testing for Friedreich’s ataxia in older people with spastic ataxia or other atypical presentations,” researchers wrote.
“Friedreich’s ataxia cannot be excluded on the basis of age and should always be considered in patients with late-onset cerebellar ataxia,” they added.
“Awareness of very-late-onset Friedrech’s ataxia prevents unnecessary investigations and promotes screening in younger relatives, who may show genetic anticipation and cardiac complications,” the study concluded.