Exome Analysis Identifies a Novel Compound Heterozygous Alteration in TGM1 Gene Leading to Lamellar Ichthyosis in a Child From Saudi Arabia: Case Presentation.

Sami Raja Alallasi,Babajan Banagnapali,Noor Ahmad Shaik,Jumana Yousuf Al-Aama,Bandar Ali Al-Shehri,Musharraf Jelani,Amal A Kokandi,Nuha Mohammad Alrayes

doi:10.3389/fped.2019.00044

Sami Raja Alallasi, Babajan Banagnapali + Show 6 more

Open Access

https://doi.org/10.3389/fped.2019.00044

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Abstract

Background: Lamellar ichthyosis is an autosomal recessive type of rare skin disorders characterized with defective epidermis leading hyperkeratosis with brownish-gray scales over the body. These patients are born as collodion babies and may also exhibit additional features like erythema, ectropion, and eclabium. This disease is mainly caused by homozygous and compound heterozygous alterations in transglutaminase 1 encoding gene (TGM1), which is located on 14q12.Case presentation: This study reports the genetic analysis of a 4-year Saudi girl presenting lamellar ichthyosis. She was the first child of unrelated parents. The family had no previous history of the disease phenotype. She was born as a collodion baby without any prenatal complications. At the time of this study she had developed rough scaly skin on her legs, arms and trunk regions with thick palms and soles. Whole exome sequencing (WES) followed by Sanger sequence validation identified a novel compound heterozygous variant in TGM1 gene. The paternal variant was a missense transition (c.1141G>A; p.Ala381Thr) present at exon 7, while maternal variant (c.758-1G>C) was present at the intron4-exon5 boundary. To the best of our knowledge these variants had not been reported before in TGM1 gene.Conclusion: In isolated and inbred populations, homozygous variants are identified more frequently; however, our results suggest that compound heterozygous variants should also be considered especially when the marriages are not consanguineous.

Highlights

Lamellar ichthyosis (LI, MIM 242300) is one of the nonsyndromic forms of ichthyoses inherited in autosomal recessive form
We applied a combination of strategies covering whole exome sequencing (WES) to identify list of altered genes involved in autosomal recessive ichthyosis (Table 1) and targeted Sanger sequencing (SS) of the short listed variants retrieved from Whole exome sequencing (WES) analysis
She was born as collodion baby on term with a normal pregnancy

Summary

Introduction

Lamellar ichthyosis (LI, MIM 242300) is one of the nonsyndromic forms of ichthyoses inherited in autosomal recessive form. Lamellar ichthyosis is an autosomal recessive type of rare skin disorders characterized with defective epidermis leading hyperkeratosis with brownish-gray scales over the body. These patients are born as collodion babies and may exhibit additional features like erythema, ectropion, and eclabium. This disease is mainly caused by homozygous and compound heterozygous alterations in transglutaminase 1 encoding gene (TGM1), which is located on 14q12. Case presentation: This study reports the genetic analysis of a 4-year Saudi girl presenting lamellar ichthyosis. She was the first child of unrelated parents. To the best of our knowledge these variants had not been reported before in TGM1 gene

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