Harlequin ichthyosis due to novel splice site mutation in the ABCA12 gene: postnatal to prenatal diagnosis.

BACKGROUND

Harlequin ichthyosis (HI) is a severe genetic disorder caused by the mutation in the ABCA12 gene. Infants born with this condition have markedly thickened, hard stratum corneum skin all over the body.

METHODS

A female child born with a thick white plate of skin with deep cracks all over the body was investigated for genes associated with congenital Ichthyosis by Next Generation sequencing. The variant relevant to the clinical indications was identified using Picard and GATK version 3.6. Variant's pathogenicity was predicted by "in silico" tools like Mutation Taster 2, Mutation Assessor and LRT. Bidirectional Sanger sequencing further validated the same variant detected in the proband and confirmed in the parental blood and CVS.

RESULTS

A homozygous 5' splice site variation that affects the position at 4 nucleotides downstream to the donor proximal splice site of intron 40 (c.5939+4A>G; ENST00000272895) of the ABCA12 gene was detected in the proband, and the parents were heterozygous for the same variant. This led to the confirmation of diagnosis of Harlequin ichthyosis in the proband. "In silico" prediction of the variant was found to be damaging by MutationTaster2. The CVS sample during subsequent pregnancy was confirmed to be heterozygous for the same variant.

CONCLUSIONS

The novel intronic mutation found in the proband confirmed the clinical diagnosis as a severe type of HI and has helped the family in providing precise genetic counseling for further prevention of the disease and carrier screening of other family members.