Infantile-onset parkinsonism, dyskinesia, and developmental delay: do not forget polyglutamine defects!

We present the phenotype of an infant with the largest ATN1 CAG expansion reported to date (98 repeats). He presented at 4 months with developmental delay, poor eye contact, acquired microcephaly, failure to thrive. He progressively developed dystonia-parkinsonism with paroxysmal oromandibular and limbs dyskinesia and fatal outcome at 17 months. Cerebral MRI disclosed globus pallidus T2-WI hyperintensities and brain atrophy. Molecular analysis was performed post-mortem following the diagnosis of dentatorubral-pallidoluysian atrophy (DRPLA) in his symptomatic father. Polyglutamine expansion defects should be considered when neurodegenerative genetic disease is suspected even in infancy and parkinsonism can be a presentation of infantile-onset DRPLA.