Variant characterisation and clinical profile in a large cohort of patients with Ellis-van Creveld syndrome and a family with Weyers acrofacial dysostosis.

BACKGROUND: Ellis-van Creveld syndrome (EvC) is a recessive disorder characterised by acromesomelic limb shortening, postaxial polydactyly, nail-teeth dysplasia and congenital cardiac defects, primarily caused by pathogenic variants in EVC or EVC2. Weyers acrofacial dysostosis (WAD) is an ultra-rare dominant condition allelic to EvC. The present work aimed to enhance current knowledge on the clinical manifestations of EvC and WAD and broaden their mutational spectrum. METHODS: We conducted molecular studies in 46 individuals from 43 unrelated families with a preliminary clinical diagnosis of EvC and 3 affected individuals from a family with WAD and retrospectively analysed clinical data. The deleterious effect of selected variants of uncertain significance was evaluated by cellular assays. MAIN RESULTS: We identified pathogenic variants in EVC/EVC2 in affected individuals from 41 of the 43 families with EvC. Patients from each of the two remaining families were found with a homozygous splicing variant in WDR35 and a de novo heterozygous frameshift variant in GLI3, respectively. The phenotype of these patients showed a remarkable overlap with EvC. A novel EVC2 C-terminal truncating variant was identified in the family with WAD. Deep phenotyping of the cohort recapitulated 'classical EvC findings' in the literature and highlighted findings previously undescribed or rarely described as part of EvC. CONCLUSIONS: This study presents the largest cohort of living patients with EvC to date, contributing to better understanding of the full clinical spectrum of EvC. We also provide comprehensive information on the EVC/EVC2 mutational landscape and add GLI3 to the list of genes associated with EvC-like phenotypes.

Clinical and molecular characteristics of 26 fetuses with lethal multiple congenital contractures.

Multiple congenital contractures (MCC) due to fetal akinesia manifest across a broad spectrum of diseases, ranging from mild distal arthrogryposis to lethal fetal akinesia deformation sequence. We hereby present a series of 26 fetuses displaying severe MCC phenotypes from 18 families and describe detailed prenatal ultrasound findings, postmortem clinical evaluations, and genetic investigations. Most common prenatal findings were abnormal facial profile (65%), central nervous system abnormalities (62%), polyhydramnios (50%), increased nuchal translucency (50%), and fetal hydrops (35%). Postmortem examinations unveiled additional anomalies including facial dysmorphisms, dysplastic skeletal changes, ichthyosis, multiple pterygia, and myopathy, allowing preliminary diagnosis of particular Mendelian disorders in multiple patients. Evaluation of the parents revealed maternal grip myotonia in one family. By exome sequencing and targeted testing, we identified causative variants in ACTC1, CHST14, COG6, DMPK, DOK7, HSPG2, KLHL7, KLHL40, KIAA1109, NEB, PSAT1, RAPSN, USP14, and WASHC5 in 15 families, and one patient with a plausible diagnosis associated with biallelic NEB variants. Three patients received a dual diagnosis. Pathogenic alterations in newly discovered genes or in previously known genes recently linked to new MCC phenotypes were observed in 44% of the cohort. Our results provide new insights into the clinical and molecular landscape of lethal MCC phenotypes.

FREM2-related Fraser syndrome with popliteal pterygium and structural central nervous system anomalies.

Fraser syndrome (FS) is a rare multiple malformation disorder characterized by cryptophthalmos, characteristic craniofacial dysmorphism, cutaneous syndactyly, malformations of the respiratory and urinary tract, and anogenital anomalies. Although the characteristic presentation of FS can be detected prenatally, oligohydramnios often challenges the clinical diagnosis. Here we report on the atypical prenatal and postmortem findings of a fetus with FS caused by a novel homozygous frameshift variant in FREM2. Our study highlights the variable manifestations of the FS and expands the clinical spectrum to include popliteal pterygium and structural central nervous system anomalies.

Clinical and molecular genetic findings of Crisponi/cold-induced sweating syndrome (CS/CISS) spectrum in patients from Turkey.

Crisponi/cold-induced sweating syndrome (CS/CISS) is a rare autosomal recessive disorder characterized by episodic hyperthermia, arthrogryposis, impaired feeding ability, and respiratory distress. The classic CS/CISS is mainly associated with CRLF1 and, rarely, CLCF1. PERCHING syndrome, previously known as CS/CISS type-3 associated with biallelic pathogenic variants in KLHL7, is notable for its few overlapping manifestations. This study presents genotype-phenotype relationships in CS/CISS-like spectrum associated with CRLF1 and KLHL7. Clinical findings of 19 patients from 14 families and four patients from three families were found in association with six different CRLF1 and three different KLHL7 variants, respectively. c.167T>C and c.713delC of the CRLF1 gene and the c.642G>C of the KLHL7 were novel. The c.708_709delCCinsT allele of CRLF1 was identified in 10 families from the Mardin province of Turkey, underlining that an ancestral haplotype has become widespread. CRLF1-associated phenotypes revealed novel manifestations such as prenatal oligohydramnios, benign external hydrocephalus, previously unreported dysmorphic features emerging with advancing age, severe palmoplantar keratoderma and facial erythema, hypopigmented macules and streaks, and recurrent cardiac arrests. KLHL7 variants presented with glabellar nevus flammeus, blepharophimosis, microcephaly, thin corpus callosum, and cleft palate. Abnormalities of sweating, observed in one patient reported herein, is known to be very rare among KLHL7-related phenotypes.

Functional loss of ubiquitin-specific protease 14 may lead to a novel distal arthrogryposis phenotype.

Multiple congenital contractures (MCC) comprise a number of rare, non-progressive conditions displaying marked phenotypic and etiologic heterogeneity. A genetic cause can be established in approximately half of the affected individuals, attributed to genetic defects in the formation and functioning of the central and peripheral nervous system, neuromuscular junctions, skeletal muscles, and connective tissue. Ubiquitin-specific protease 14 (USP14) encodes a major proteasome-associated deubiquitinating enzyme with an established dual role as an inhibitor and an activator of proteolysis, maintaining protein homeostasis. Usp14-deficient mice show a phenotype similar to lethal human MCC phenotypes, with callosal anomalies, muscle wasting, and early lethality, attributed to neuromuscular junction defects due to decreased monomeric ubiquitin pool. We describe a new, autosomal recessive MCC phenotype in three fetuses from two different branches of a consanguineous family, presenting with distal arthrogryposis, underdevelopment of the corpus callosum, and dysmorphic facial features. Exome sequencing identified a biallelic 4-bp deletion (c.233_236delTTCC; p.Leu78Glnfs*11, SCV002028347) in USP14, and sequencing of family members showed segregation with the phenotype. RT-qPCR experiment in an unaffected heterozygote revealed that mutant USP14 was expressed, indicating that abnormal transcript escapes nonsense-mediated mRNA decay. We propose that herein described fetuses represent the first human phenotype of USP14 loss, with callosal anomalies and/or cortical malformations, multiple contractures, and recognizable dysmorphic facial features.

Antenatal diagnostic dilemma in a pseudodominant pedigree with lamin-B receptor (LBR)-related regressive spondylometaphyseal dysplasia.

The lamin-B receptor (LBR) encodes a dual-functioning inner nuclear membrane protein essential for cholesterol biosynthesis and chromatin organization. LBR pathogenic variants cause distinct phenotypes due to the dual function of LBR, including Pelger-Huët anomaly (PHA), PHA with mild skeletal anomalies (PHASK; MIM# 618019), LBR-related regressive type of spondylometaphyseal dysplasia (LBR-R-SMD), Greenberg dysplasia (MIM# 215140). We here report the first case with radiological manifestations of LBR-R-SMD in the fetal period, and milder skeletal findings in the similarly affected father. Direct sequencing of LBR revealed homozygous c.1534C>T (p.Arg512Trp) in exon 12 in both affected individuals. Our report further refines the early phenotype in LBR-R-SMD, and demonstrates that the p.Arg512Trp mutation is associated with PHA. We propose that LBR-R-SMD should be considered as a differential diagnosis in pregnancies with sonographic evidence of short and bowed tubular bones with narrow thorax. Evaluating peripheral blood smears of expectant parents for the presence of PHA may lead to a clinical diagnosis, allowing for comprehensive prenatal genetic counseling.