In terms of prevalence, 11β-hydroxylase deficiency (11β-OHD), a common form of congenital adrenal hyperplasia, closely follows 21-hydroxylase deficiency. 11β-OHD has been attributed to diminished enzymatic activity owing to CYP11B1 gene variants, mainly encompassing single nucleotide variations and insertions-deletions. The involvement of chimeric CYP11B2/CYP11B1 genes in 11β-OHD has rarely been reported. We conducted a genetic investigation on a male infant with generalized pigmentation and abnormal steroid hormone levels. Whole-exome sequencing revealed a heterozygous variant in CYP11B1 inherited from the mother (NM_000497.4: c.1391_1393dup [p.Leu464dup]). Long-range polymerase chain reaction revealed an additional allele, a chimeric CYP11B2/CYP11B1 gene, inherited from the father. The current case report highlights the need to consider the occurrence of gene fusion variants in the diagnosis of neonatal or early infantile 11β-OHD.
