Inspired by a patient
Jansen S, van der Werf IM, Innes AM, Afenjar A, Agrawal PB, Anderson IJ, Atwal PS, van Binsbergen E, van den Boogaard MJ, Castiglia L, Coban-Akdemir ZH, van Dijck A, Doummar D, van Eerde AM, van Essen AJ, van Gassen KL, Guillen Sacoto MJ, van Haelst MM, Iossifov I, Jackson JL, Judd E, Kaiwar C, Keren B, Klee EW, Klein Wassink-Ruiter JS, Meuwissen ME, Monaghan KG, de Munnik SA, Nava C, Ockeloen CW, Pettinato R, Racher H, Rinne T, Romano C, Sanders VR, Schnur RE, Smeets EJ, Stegmann APA, Stray-Pedersen A, Sweetser DA, Terhal PA, Tveten K, VanNoy GE, de Vries PF, Waxler JL, Willing M, Pfundt R, Veltman JA, Kooy RF, Vissers LELM, de Vries BBA. De novo variants in FBXO11 cause a syndromic form of intellectual disability with behavioral problems and dysmorphisms. Eur J Hum Genet. 2019 May;27(5):738-746. doi: 10.1038/s41431-018-0292-2. Epub 2019 Jan 24. PMID: 30679813; PMCID: PMC6462006
Determining pathogenicity of genomic variation identified by next-generation sequencing techniques can be supported by recurrent disruptive variants in the same gene in phenotypically similar individuals. However, interpretation of novel variants in a specific gene in individuals with mild-moderate intellectual disability (ID) without recognizable syndromic features can be challenging and reverse phenotyping is often required. We describe 24 individuals with a de novo disease-causing variant in, or partial deletion of, the F-box only protein 11 gene (FBXO11, also known as VIT1 and PRMT9). FBXO11 is part of the SCF (SKP1-cullin-F-box) complex, a multi-protein E3 ubiquitin-ligase complex catalyzing the ubiquitination of proteins destined for proteasomal degradation. Twenty-two variants were identified by next-generation sequencing, comprising 2 in-frame deletions, 11 missense variants, 1 canonical splice site variant, and 8 nonsense or frameshift variants leading to a truncated protein or degraded transcript. The remaining two variants were identified by array-comparative genomic hybridization and consisted of a partial deletion of FBXO11. All individuals had borderline to severe ID and behavioral problems (autism spectrum disorder, attention-deficit/hyperactivity disorder, anxiety, aggression) were observed in most of them. The most relevant common facial features included a thin upper lip and a broad prominent space between the paramedian peaks of the upper lip. Other features were hypotonia and hyperlaxity of the joints. We show that de novo variants in FBXO11 cause a syndromic form of ID. The current series show the power of reverse phenotyping in the interpretation of novel genetic variances in individuals who initially did not appear to have a clear recognizable phenotype.
Lee CG, Seol CA, Ki CS. The first familial case of inherited intellectual developmental disorder with dysmorphic facies and behavioral abnormalities (IDDFBA) with a novel FBXO11 variant. Am J Med Genet A. 2020 Nov;182(11):2788-2792. doi: 10.1002/ajmg.a.61828. Epub 2020 Sep 9. PMID: 32902151.
Intellectual developmental disorder with dysmorphic facies and behavioral abnormalities (IDDFBA) caused by germline de novo variants in FBXO11 was recently recognized as a novel intellectual disability (ID) syndrome through reverse phenotyping after whole-exome sequencing (WES). Fewer than 50 disease-causing de novo FBXO11 variants in IDDFBA are reported thus far. Here, we present the first report of a family showing autosomal dominantly inherited IDDFBA, harboring a novel heterozygous variant in FBXO11 (c.2401_2405dup;p. Gly803Leufs*6) identified by WES. In this family, the mother and two daughters showed mild ID and mild facial dysmorphism. This finding is expected to increase our understanding of the genotype-phenotype of IDDFBA and to facilitate genetic counseling for the disorder caused by FBXO11.
Silva RG, Dupont J, Silva E, Sousa AB. New ocular findings in a patient with a novel pathogenic variant in the FBXO11 gene. J AAPOS. 2022 Oct;26(5):268-270. doi: 10.1016/j.jaapos.2022.05.008. Epub 2022 Aug 5. PMID: 35940561.
Intellectual developmental disorder with dysmorphic facies and behavioral abnormalities (IDDFBA) is a recently described autosomal dominant entity caused by pathogenic variants, mostly de novo, in the FBXO11 gene. It presents in the first years of life with highly variable clinical manifestations. The main features of IDDFBA include borderline-to-severe intellectual disability, behavioral problems, hypotonia, facial dysmorphisms, minor skeletal abnormalities, and recurrent infections. Although eye problems, such as refractive errors, eye misalignment and minor visual changes, have been described in about 48% of patients, a major ocular defect, namely, bilateral optic nerve hypoplasia, has been reported in the literature only once. We report an 8-year-old boy with a novel de novo pathogenic variant in FBXO11 gene (NM_001190274.1: c.1166dup, p.Cys390Metfs∗3) and a complex ophthalmological phenotype, consisting of right microphthalmia, very shallow anterior chamber, and persistent pupillary membrane, right dense nuclear cataract, bilateral optic nerve hypoplasia, and bilateral horizontal manifest nystagmus.