A girl with infantile neuronal ceroid lipofuscinosis caused by novel PPT1 mutation and paternal uniparental isodisomy of chromosome 1.

Infantile neuronal ceroid lipofuscinosis (INCL) is an autosomal recessive disorder starting in infancy as early as 12-month-old, caused by PPT1 (palmitoyl-protein thioesterase 1) mutations, and characterized by progressive psychomotor deterioration, brain atrophy, myoclonic jerk and visual impairment. INCL can be diagnosed by brain magnetic resonance image (MRI) prior to rapid deterioration stage. To date, there is no INCL patient whose manifestation was caused by uniparental isodisomy (UPiD). We reported a girl diagnosed with INCL. Genetic analysis revealed a novel PPT1 mutation c.20_47del28:p.Leu7Hisfs*21. Only the father of the patient was found as a carrier of this mutation. SNP array showed the mutation became homozygous by paternal UPiD of chromosome 1. Although ICNL is a rare disease except in Finland, it is not difficult to diagnose it since the clinical symptoms and MRI findings are characteristic. Genetic testing is useful for definitive diagnosis, and distinction of UPiD is essential for genetic counseling.