Massive SCA7 expansion detected in a 7-month-old male with hypotonia, cardiomegaly, and renal compromise.

Infantile spinocerebellar ataxia type 7 (SCA7) is phenotypically different from the child-onset and adult-onset cases, presenting as a multisystem disorder associated with pathologically large CAG trinucleotide repeat sequences. We describe a case study of a male who presented at 5 months of age with marked motor delay, failure to thrive, and a patent ductus arteriosus. He later developed renal failure of uncertain aetiology. The infant became progressively hypotonic, and cardiac and renal function deteriorated further; he died at the age of 11 months of multisystem failure. Family history revealed a diagnosis of SCA7 in the infant's father, paternal grandfather, and aunt. DNA analysis confirmed an expanded trinucleotide repeat in the SCA7 locus of about 240 repeats, suggesting a diagnosis of infantile SCA7. Striking anticipation is seen in SCA7, particularly with paternal transmission. The underlying pathophysiological processes seem to involve alteration in transcriptional regulation and a selective neuronal vulnerability to the widely distributed abnormal protein product. This case report reviews the current literature relating to infantile SCA7 and raises awareness of this rare but important phenotype.