Paternal uniparental disomy of chromosome 2 resulting in a concurrent presentation of Crigler–Najjar syndrome type I and long‐chain 3‐hydroxyacyl‐CoA dehydrogenase deficiency

This is the first report of the concurrent development of long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD) and Crigler-Najjar syndrome type 1 (CNs1) inherited via uniparental disomy of chromosome 2, which are both autosomal recessive pathologies. Through an expanded newborn metabolic panel, a male infant was identified as having an acylcarnitine pattern typical for LCHADD, later confirmed to be caused by a well-characterized pathogenic variant in the HADHA gene located at 2p23. Prolonged non-hematologic jaundice requiring repetitive phototherapy prompted further genetic analysis, leading to the identification of another genetic abnormality consistent with CNs1, which was caused by a novel pathogenic variant in the UGT1A1 gene located at 2q37. The two identified point mutations in chromosome 2 were homozygous and present on separate arms, which indicated potential uniparental disomy. Microarray analysis of the genetic material from the patient and his parents confirmed paternal isodisomy of chromosome 2. Further studies are needed to identify other possible pathogenic variants located on the same defective chromosome, evaluate the combined effect of the two metabolic abnormalities, and plan the best possible treatment and care.