Expanding the Phenotype of the <i>FAM149B1</i>-Related Ciliopathy and Identification of Three Neurogenetic Disorders in a Single Family
Biallelic truncating <i>FAM149B1</i> variants result in cilia dysfunction and have been reported in four infants with Joubert syndrome and orofaciodigital syndrome type VI, respectively. We report here on three adult siblings, 18 to 40 years of age, homozygous for the known <i>FAM1...
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| Main Authors: | , , , , , , , |
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| Format: | article |
| Language: | EN |
| Published: |
MDPI AG
2021
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| Subjects: | |
| Online Access: | https://doaj.org/article/455b181e07fb4e8aa99e18ee1bbd1fc7 |
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| Summary: | Biallelic truncating <i>FAM149B1</i> variants result in cilia dysfunction and have been reported in four infants with Joubert syndrome and orofaciodigital syndrome type VI, respectively. We report here on three adult siblings, 18 to 40 years of age, homozygous for the known <i>FAM149B1</i> c.354_357delinsCACTC (p.Gln118Hisfs*20) variant. Detailed clinical examinations were performed including ocular and gait analyses, skeletal- and neuroimaging. All three patients presented with neurological and oculomotor symptoms since birth and mild skeletal dysplasia in infancy resulting in characteristic gait abnormalities. We document mild skeletal dysplasia, abnormal gait with increased hip rotation and increased external foot rotation, ataxia, variable polydactyly, ocular Duane syndrome, progressive ophthalmoplegia, nystagmus, situs inversus of the retinal vessels, olfactory bulb aplasia, and corpus callosal dysgenesis as novel features in <i>FAM149B1</i>-ciliopathy. We show that intellectual disability is mild to moderate and retinal, renal and liver function is normal in these affected adults. Our study thus expands the <i>FAM149B1</i>-related Joubert syndrome to a mainly neurological and skeletal ciliopathy phenotype with predominant oculomotor dysfunction but otherwise stable outcome in adults. Diagnosis of <i>FAM149B1</i>-related disorder was impeded by segregation of multiple neurogenetic disorders in the same family, highlighting the importance of extended clinical and genetic studies in families with complex phenotypes. |
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