Nonneurological Involvement in Late-Onset Friedreich Ataxia (LOFA): Exploring the Phenotypes

Abstract

Friedreich's ataxia (FDRA) is the most common inherited ataxia worldwide, caused by homozygous GAA expansions in the FXN gene. Patients usually have early onset ataxia, areflexia, Babinski sign, scoliosis and pes cavus, but at least 25 % of cases have atypical phenotypes. Disease begins after the age of 25 in occasional patients (late-onset Friedreich ataxia (LOFA)). Little is known about the frequency and clinical profile of LOFA patients. One hundred six patients with molecular confirmation of FDRA and followed in three Brazilian outpatient centers were enrolled. General demographics, GAA expansion size, age at onset, cardiac, endocrine, and skeletal manifestations were evaluated and compared between LOFA and classic FDRA (cFDRA) groups. We used Mann-Whitney and Fisher tests to compare means and proportions between groups; p values <0.05 were considered significant. LOFA accounted for 17 % (18/106) and cFDRA for 83 % (88/106) of the patients. There were 13 and 48 women in each group, respectively. LOFA patients were significantly older and had smaller GAA expansions. Clinically, LOFA group had a tendency toward lower frequency of diabetes/impaired glucose tolerance (5.8 vs. 17 %, p = 0.29) and cardiomyopathy (16.6 vs. 28.4 %, p = 0.38). Skeletal abnormalities were significantly less frequent in LOFA (scoliosis 22 vs. 61 %, p = 0.003, and pes cavus 22 vs.75 %, p < 0.001) as were spasticity and sustained reflexes, found in 22 % of LOFA patients but in none of the cFDRA patients (p = 0.001). LOFA accounts for 17 % of Brazilian FDRA patients evaluated herein. Clinically, orthopedic features and spasticity with retained reflexes are helpful tips to differentiate LOFA from cFDRA patients.

Keywords: Ataxia; Late-onset Friedreich ataxia; Retained reflexes; Spastic ataxia.