Characterization of TGM1 c.984+1G>A mutation identified in a homozygous carrier of lamellar ichthyosis

Compound Heterozygous Mutations in TGM1 Causing a Severe Form of Lamellar Ichthyosis: A Case Report

We aimed to detect the pathogenic gene mutations in a patient with lamellar ichthyosis (LI). The genomic DNA of the patient was examined using high-throughput whole-exome sequencing to identify the causative mutations. Compound heterozygous mutations of c.1187G>T (p.Arg396Leu) and c.607C>T (p.Gln203*) were found in the transglutaminase-1 gene (TGM1) on chromosome 14 of the proband. The mutations stated above have been reported to impair the function of TGM1 protein and to be pathogenic. Our data suggest that the proband carried compound heterozygous mutations of c.1187G>T(p.Arg396Leu) and c.607C>T(p.Gln203*) in TGM1, which were in the trans position and the cause of his disease. We also found some dermoscopic in this patient which may be specific in LI.

Novel Homozygous Mutations in the Genes TGM1, SULT2B1, SPINK5 and FLG in Four Families Underlying Congenital Ichthyosis

Background: Ichthyoses are a large group of hereditary cornification disorders, which are both clinically and etiologically heterogeneous and affect mostly all the skin surface of the patients. Ichthyosis has its origin in an ancient Greek word “ichthys” meaning fish, this is because the ichthyosis patients have dry, thickened, and scaly skin. There is an excess accumulation of epidermal cells resulting in the appearance of continuous and widespread scales on the body. There are many varieties of ichthyosis with a broad spectrum of intensity, severity, and associated symptoms, most of them are extremely rare. Ichthyosis vulgaris is the most frequently occurring type of ichthyoses. Method: The present study consists of four Pakistani ichthyosis families (A, B, C, and D). Whole exome sequencing (WES) approach was used to identify the pathogenic sequence variants in probands. The segregation of these variants in other participants was confirmed by Sanger sequencing. Results: Total four variants including, two splice site (TGM1: c.2088 + 1G > A) and (SPINK5: c.882 + 1G > T), a missense (SULT2B1: c.419C > T; p. Ala140Val), and a nonsense (FLG: c.6109C > T; p. Arg2037Ter) variant were identified in families A, C, B, and D, respectively, as causative mutations responsible for ichthyosis in these families. Conclusion: Our study unravels the molecular etiology of the four Pakistani ichthyosis families and validates the involvement of TGM1, SULT2B1, SPINK5, and FLG, in the etiology of different forms of ichthyosis. In addition, this study also aims to give a detailed clinical report of the studied ichthyosis families.

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

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.

Collodion Baby with TGM1 gene mutation

Collodion baby (CB) is normally diagnosed at the time of birth and refers to a newborn infant that is delivered with a lambskin-like membrane encompassing the total body surface. CB is not a specific disease entity, but is a common phenotype in conditions like harlequin ichthyosis, lamellar ichthyosis, nonbullous congenital ichthyosiform erythroderma, and trichothiodystrophy. We report a CB that was brought to our department and later diagnosed to have TGM1 gene c.984+1G>A mutation. However, it could not be ascertained whether the infant had lamellar ichthyosis or congenital ichthyosiform erythroderma (both having the same mutation). The infant was lost to follow-up.

Autosomal recessive congenital ichthyosis

The term autosomal recessive congenital ichthyosis (ARCI) refers to a group of rare disorders of keratinization classified as nonsyndromic forms of ichthyosis. This group was traditionally divided into lamellar ichthyosis (LI) and congenital ichthyosiform erythroderma (CIE) but today it also includes harlequin ichthyosis, self-healing collodion baby, acral self-healing collodion baby, and bathing suit ichthyosis. The combined prevalence of LI and CIE has been estimated at 1 case per 138 000 to 300 000 population. In some countries or regions, such as Norway and the coast of Galicia, the prevalence may be higher due to founder effects. ARCI is genetically highly heterogeneous and has been associated with 6 genes to date: TGM1, ALOXE3, ALOX12B, NIPAL4, CYP4F22, and ABCA12. In this article, we review the current knowledge on ARCI, with a focus on clinical, histological, ultrastructural, genetic, molecular, and treatment-related aspects.

Transglutaminase-1 mutations in Omani families with lamellar ichthyosis

OBJECTIVE

To determine the molecular basis of familial ichthyosis in three Omani families.

SUBJECTS AND METHODS

Nine patients from three consanguineous families, A, B, and C, were born with typical features of lamellar ichthyosis subtype including collodion membrane and maintained ectropion, and epidermal scaling through their childhood. The 4 patients from family B had more severe symptoms requiring neonatal critical care and subsequent regular treatment with emollients, eye lubricants, and low-dose acitretin. DNA was extracted from peripheral blood by standard methods. The samples were initially genotyped to screen known loci linked to recessive ichthyosis on chromosomes 2q33-32 (ABCA12), 14q11 (TGM1), and 19p12-q12 using commercially supplied polymorphic fluorescent microsatellite markers. TGM1 was analyzed by direct sequencing for disease-associated mutations.

RESULTS

Two known pathogenic mutations in TGM1 were detected: p.Gly278Arg in families A and B and p.Arg396His in family C. These two mutations were segregating in an autosomal recessive mode of inheritance.

CONCLUSION

Two known pathogenic TGM1 mutations were detected in three large consanguineous Omani families with lamellar ichthyosis. This study confirmed the geographic distribution of known mutations to an apparently unrelated population.