First Case of Macrocephaly, Dysmorphic Facies, and Psychomotor Retardation Harboring Co-inherited Variants in HERC1...

Here, we report a case with concomitant variants: a novel homozygous HERC1 gene variant and a novel heterozygous PMP22 duplication. The 2-year-old male presented with seizures, developmental delay, macrocephaly, hypotonia, unilateral hypertrophy, thoracic scoliosis, normal brain MRI, and elevated homocysteine level which normalized after treatment. Whole exome sequencing (WES) revealed a co-occurrence of a homozygous novel likely pathogenic variant in the HERC1 gene (NM_003922.3:c.1280dup (p.ILe469Aspfs*33) and a novel heterozygous large duplication of exon 1-5 in the PMP22 gene, which has not been reported previously. The case underscores the challenges in understanding genotype-phenotype correlations and suggests a potential interplay between these genetic variants in shaping the current and future clinical phenotype of the patient. In the case of genetic diseases, this event may have important implications on family members' counseling, and concomitant variants in Charcot-Marie-Tooth (CMT) families should be considered when significant intra-familial clinical heterogeneity is observed.