Compound heterozygous PNPLA6 mutations cause Boucher-Neuhaeuser syndrome with late-onset ataxia

PNPLA6 mutations, known to be associated with the development of motor neuron phenotypes, have recently been identified in families with Boucher-Neuhaeuser syndrome. Boucher-Neuhaeuser is a rare autosomal recessive syndrome characterized by the co-occurrence of cerebellar ataxia, hypogonadotropic hypogonadism, and chorioretinal dystrophy. Gait ataxia in Boucher-Neuhaeuser usually manifests before early adulthood, although onset in the third or fourth decade has also been reported. However, given the recent identification of PNPLA6 mutations as the cause of this condition, the determining factors of age of symptom onset still need to be established. Here, we have identified a sporadic Boucher-Neuhaeuser case with late-onset gait ataxia and relatively milder retinal changes due to compound heterozygous PNPLA6 mutations. Compound heterozygosity was confirmed by cloning and sequencing the patient's genomic DNA from coding exons 26-29. Furthermore, both mutations (one novel and one known) fell in the phospholipase esterase domain, where most pathogenic mutations seem to cluster. Taken together, we herein confirm PNPLA6 mutations as the leading cause of Boucher-Neuhaeuser syndrome and suggest inquiring about a history of hypogonadism or visual changes in patients presenting with late-onset gait ataxia. We also advocate for neuroophthalmologic evaluation in suspected cases.