Supplementary Material for: Meckel–Gruber syndrome due to homozygous c.16del (p.Leu6SerfsTer15) variant in the TCTN1: first case from Türkiye

Introduction: Meckel–Gruber syndrome (MKS) is a clinically and genetically heterogeneous ciliopathy characterized by a triad of occipital encephalocele, polycystic kidneys, and postaxial polydactyly. Almost all of them are lethal in the prenatal or first postnatal periods. It is usually diagnosed clinically with a detailed prenatal ultrasound examination. Variants have been reported in at least 14 different genes.
Case Presentation: We report a male fetus with oligohydramnios, large kidneys with microcysts covering the entire abdomen, postaxial polydactyly of the hands, bilateral pes equinovarus, encephalocele, microphthalmia, short extremities, and a mass lesion under the diaphragm. Termination was recommended to the family due to severe findings. Fetal skin biopsy and parental peripheral blood samples were obtained to investigate the potential pathogenic variants associated with MKS via clinical exome sequencing and Sanger sequencing.
Results and Conclusion: The fetus was homozygous for the c.16del (p.Leu6SerfsTer15) variant in the TCTN1 (NM_001082538.3), and both parents were heterozygous for the variant. Genetic diagnosis is very important in terms of counseling for subsequent pregnancies. To our knowledge, this is the third Meckel Gruber case in the literature caused by the TCTN1, and a novel likely pathogenic variant was detected.