Aarskog-Scott syndrome: first report of a duplication in the FGD1 gene

Novel truncating variants in FGD1 detected in two Danish families with Aarskog-Scott syndrome and myopathic features

Aarskog–Scott syndrome (AAS) is a developmental disorder, caused by disease‐causing hemizygous variants in the FGD1 gene. AAS is characterized by dysmorphic features, genital malformation, skeletal anomalies, and in some cases, intellectual disability and behavioral difficulties. Myopathy has only been reported once in two affected siblings diagnosed with AAS. Only few adult cases have been reported. This article reports four adults with AAS (three male cases and one female carrier) from two unrelated Danish families, all males presented with variable features suggestive of myopathy. All four carried novel hemizygous pathogenic variants in the FGD1 gene; one family presented with the c.2266dup, p.Cys756Leufs*19 variant while the c.527dup; p.Leu177Thrfs*40 variant was detected in the second family. All males had some mild myopathic symptoms or histological abnormalities. Case 1 had the most severe myopathic phenotype with prominent proximal muscular fatigue and exercise intolerance. In addition, he had multiple deletions of mtDNA and low respiratory chain activity. His younger nephew, case 3, had difficulties doing sports in his youth and had a mildly abnormal muscle biopsy and relatively decreased mitochondrial enzyme activity. The singular case from family 2 (case 4), had a mildly myopathic muscle biopsy, but no overt myopathic symptoms. Our findings suggest that myopathic involvement should be considered in AAS.

The Prevalence of Clinical Features in Patients with Aarskog-Scott Syndrome and Assessment of Genotype-Phenotype Correlation: A Systematic Review

Aarskog–Scott syndrome is a genetically and clinically heterogeneous rare condition caused by a pathogenic variant in the FGD1 gene. A systematic review was carried out to analyse the prevalence of clinical manifestations found in patients, as well as to evaluate the genotype-phenotype correlation. The results obtained show that clinical findings of the craniofacial, orthopaedic, and genitourinary tract correspond to the highest scores of prevalence. The authors reclassified the primary, secondary, and additional criteria based on their prevalence. Furthermore, it was possible to observe, in accordance with previous reports, that the reported phenotypes do not present a direct relation to the underlying genotypes.

Novel variant in the FGD1 gene causing Aarskog-Scott syndrome

Aarskog-Scott syndrome (ASS) is a rare, X-linked recessive inherited disorder. Affected individuals may develop short stature and exhibit distinctive skeletal and genital development. Mutations in the FYVE, rhogef and pleckstrin homology domain-containing protein 1 (FGD1) gene, located within the Xp11.21 region, are responsible for the occurrence of ASS. Since it is rare and complex, it can take a long time to obtain a definitive clinical diagnosis unless clinicians are familiar with the disease. In the present study, whole-exome sequencing (WES) was performed to screen for causal variants in a Chinese pediatric patient who exhibited a number of clinical symptoms of ASS, including short stature, facial abnormalities, stubby metacarpals and swollen testis. DNA sequencing revealed a novel c.1270 A>G mutation in exon 6 of the FGD1 gene, which led to an amino acid conversion of asparagine to aspartic acid on codon 424 and in silico analysis indicated that this novel missense mutation was pathogenic. The present study identified a novel variant of the FGD1 gene and to the best of our knowledge, is the first report of ASS in a Chinese individual. The results indicated that WES is an effective tool for the diagnosis of rare and complex syndromes such as ASS.

A novel splice site mutation of FGD1 gene in an Aarskog-Scott syndrome patient with a large anterior fontanel

Aarskog-Scott syndrome (ASS) is a rare X-linked recessive genetic disorder caused by FGD1 mutations. FGD1 regulates the actin cytoskeleton and regulates cell growth and differentiation by activating the c-Jun N-terminal kinase signaling cascade. ASS is characterized by craniofacial dysmorphism, short stature, interdigital webbing and shawl scrotum. However, there is a wide phenotypic heterogeneity because of the additional clinical features. ASS and some syndromes including the autosomal dominant inherited form of Robinow syndrome, Noonan syndrome, pseudohypoparathyroidism, Silver-Russel and SHORT syndrome have some overlapping phenotypic features. Herein, we report a patient with ASS and a large anterior fontanel who was initially diagnosed as Robinow syndrome. He was found to have a novel c.1340+2 T>A splice site mutation on the FGD1 gene.

Aarskog-Scott syndrome: a novel mutation in the FGD1 gene associated with severe craniofacial dysplasia

Aarskog syndrome (AAS) is an X-linked human disease that affects the skeletal formation and embryonic morphogenesis and is caused by mutations in the FGD1 gene. Patients typically show distinctive skeletal and genital developmental abnormalities, but a broad spectrum of clinical phenotypes has been observed. We report here on the clinical and molecular analysis of a family that reveals a novel FGD1 mutation in a 9-year-old boy displaying extreme craniofacial dysplasia associated with attention deficit hyperactivity disorder. Sequencing of FGD1 revealed a novel mutation in exon 7 at position c.1468 C > T in the index patient, leading to a stop codon in the highly conserved RhoGEF gene domain. His mother and maternal grandmother were also found to be heterozygous for this FGD1 mutation.

CONCLUSION

Our results identify a novel mutation of FDG1 in a family with Aarskog syndrome and underscore the phenotypical variability of this condition.