Harlequin ichthyosis: a novel compound mutation of ABCA12 with prenatal diagnosis

Case Report: Prenatal Diagnosis of a Fetus With Harlequin Ichthyosis Identifies Novel Compound Heterozygous Variants: A Case Report

Background

Harlequin ichthyosis (HI) is the most severe form of the keratinizing disorders, and it is characterized by whole-body hard stratum corneum. ABCA12 has been identified as the major disease-causing gene of HI.

Methods

A case of HI was prenatally diagnosed by ultrasonography and genetic tests. The fetus had been found with dentofacial deformity and profound thickening of the palm and plantar soft tissues. Chromosomal microarray analysis (CMA) and whole exome sequencing (WES) were then performed on the amniotic fluid to identify germline pathogenic variants for the fetus. Candidate variants were verified by Sanger sequencing.

Results

Compound heterozygous frameshift variants (p.Q719QfsX21; p.F2286LfsX6) of ABCA12 were identified for the fetus, suggesting the former variants were maternally inherited and the latter paternally inherited. The fetus was terminated.

Conclusion

A prenatal molecular diagnosis is an important approach for the prevention of HI. In the study, we provided a successful case of genetic counseling for a family with an HI baby.

An ABCA12 missense variant in a Shorthorn calf with ichthyosis fetalis

Two clinical forms of ichthyosis in cattle have been reported, ichthyosis fetalis and congenital ichthyosis. Ichthyosis poses animal welfare and economic issues and the more severe form, ichthyosis fetalis, is lethal. A Shorthorn calf with ichthyosis fetalis was investigated and a likely causal missense variant on chromosome 2 in the ABCA12 gene (NM_001191294.2:c.6776T>C) was identified by whole genome sequencing. Mutations in the ABCA12 gene are known to cause ichthyosis fetalis in cattle and Harlequin ichthyosis in humans. Sanger sequencing of the affected calf and the dam confirmed the variant was homozygous in the affected calf and heterozygous in the dam. Further genotyping of 130 Shorthorn animals from the same property revealed an estimated allele frequency of 3.8%. The presented findings enable genetic testing for breeding and diagnostics.

A novel ABCA12 pathologic variant identified in an Ecuadorian harlequin ichthyosis patient: A step forward in genotype-phenotype correlations

Background

Autosomal recessive congenital ichthyoses (ARCI) have been associated with different phenotypes including: harlequin ichthyosis (HI), congenital ichthyosiform erythroderma (CIE), and lamellar ichthyosis (LI). While pathogenic variants in all ARCI genes are associated with LI and CIE phenotypes, the unique gene associated with HI is ABCA12. In HI, the most severe ARCI form, pathogenic variants in both ABCA12 gene alleles usually have a severe impact on protein function. The presence of at least one non‐truncating variant frequently causes a less severe congenital ichthyosis phenotype (LI and CIE).

Methods

We report the case of a 4‐year‐old Ecuadorian boy with a severe skin disease. Genetic diagnosis was performed by NGS. In silico predictions were performed using Alamut software v2.11. A review of the literature was carried out to identify all patients carrying ABCA12 splice‐site and missense variants, and to explore their genotype‐phenotype correlations.

Results

Genetic testing revealed a nonsense substitution, p.(Arg2204*), and a new missense variant, p.(Val1927Leu), in the ABCA12 gene. After performing in silico analysis and a comprehensive review of the literature, we conclude that p.(Val1927Leu) affects a well conserved residue which could either disturb the protein function or alter the splicing process, both alternatives could explain the severe phenotype of our patient.

Conclusion

This case expands the spectrum of ABCA12 reported disease‐causing variants which is important to unravel genotype‐phenotype correlations and highlights the importance of missense variants in the development of HI.

Prenatal diagnose of a fetus with Harlequin ichthyosis in a Chinese family

OBJECTIVE

Harlequin ichthyosis (HI) was the most severe form of ichthyoses, which leaded to neonatal death in 50% of cases. It was the result of mutations in ABCA12 gene. With the development of ultrasound skills and genetic analysis, HI could be prenatal diagnosed.

CASE REPORT

Here, we reported a case of HI, which was prenatal diagnosed by ultrasound examination and genetic analysis. The fetus was found that severe ectropion, eclabium, flattened nose, and rudimentary ears by ultrasound at 20 weeks gestation. A molecular genetic analysis was performed and revealed two mutations in the ABCA12 gene. One of two mutations were not reported in the past. The fetus was terminated.

CONCLUSION

HI was associated with the poor prognosis of HI neonates. Prenatal ultrasound and genetic analysis were important for prenatal diagnosis of HI and were helpful to give sufficient prenatal counsels for the family with HI baby.