Years published: 2023
NORD gratefully acknowledges Cara Skraban, MD, Associate Professor of Clinical Pediatrics, Perelman School of Medicine at the University of Pennsylvania, Attending Physician, Division of Human Genetics, Children’s Hospital of Philadelphia, and the Skraban-Deardoff Syndrome Foundation for the preparation of this report.
WDR26-related disorder, also known as Skraban-Deardorff syndrome (SKDEAS), is a rare neurodevelopmental disorder caused by changes (variants or mutations) in the gene WDR26. Individuals with SKDEAS can present with a variety of symptoms that commonly include differences in development, seizures, low muscle tone, friendly personality and unique facial features. Most individuals have a new (de novo) change in the WDR26 gene that is not inherited. WDR26-related disorder follows an autosomal dominant inheritance pattern, meaning that someone with the condition has a 50% risk of passing the gene variant to each child. There is no specific treatment for the condition and management is based on an individual’s symptoms with particular focus on attainment of developmental milestones.
The symptoms of WDR26-related disorder vary among individuals. Not every person with the syndrome exhibits all of the symptoms or exhibits them in the same way. Symptoms can include:
Developmental delay and intellectual disability
• People with WDR26-related disorder have varying degrees of developmental delays and intellectual disabilities ranging from mild to severe.
• Speech delays are typical, particularly in expressive language.
• Delays in the development of motor skills including sitting and walking are common. Many individuals walk with a wide-based, spastic, stiff-legged gait.
• Some individuals have repetitive (stereotypical) movements and autistic features. Some have a formal diagnosis of autism spectrum disorder. Most are described as happy and socially engaging.
• All individuals in the initially reported group (Skraban et al, 2017) had a history of seizures. Since then, many individuals without epilepsy have been identified, but seizures still remain common. Some of the seizures were triggered by fever (febrile seizures); others were not. Some patients received treatment with antiepileptic medications, which typically brought the seizures under control.
• Minor structural brain malformations have been identified in some people.
• Decreased muscle tone (hypotonia) is common.
• People with WDR26-related disorder typically share a set of subtle facial characteristics, though not every individual with the diagnosis exhibits all of them. These characteristics can include:
o prominent upper lip and upper jawbone
o wide mouth
o prominent gums
o widely spaced teeth
o mildly coarse facial features
o broad nasal tip
Other health differences
• People with WDR26-related disorder can have a variety of other health issues. Some of these include:
o Feeding issues/poor growth
o Ophthalmologic (eye and vision) differences
o Structural heart differences
o Skeletal differences
o Cleft palate
o Genitourinary differences
o Recurrent infections
o Sleep issues
WDR26-related disorder is caused by changes (variants or mutations) in the WDR26 gene. In the individuals identified to date, the vast majority are de novo WDR26 gene variants. This means that the variants are not inherited from either parent, but instead are random variants that occur in a parent’s single egg or sperm prior to conception or during early embryologic development. The variants are heterozygous, which means that only one of two copies of an individual’s WDR26 gene has the variant.
The exact number of individuals WDR26-related disorder is unknown and this condition is likely underrecognized. It affects both males and females and has been identified in people from all over the world.
WDR26-related disorder may be suspected based on the signs and symptoms associated with the disorder. The diagnosis is confirmed with molecular genetic testing that shows a disease-causing variant in the WDR26 gene.
Currently, there is no specific treatment for WDR26-related disorder. Care focuses on the individual’s symptoms. The medical team typically includes a genetic specialist, a neurologist and a developmental pediatrician, with other specialists involved as symptoms warrant. Early therapy is encouraged (physical, occupational, speech therapy) to ensure that the child achieves to the best of their abilities. Applied Behavior Analysis (ABA) therapy has been beneficial for some individuals.
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Hu J, Xu M, Zhu X, and Zhang Y. Two novel variants of WDR26 in Chinese patients with intellectual disability. Genes. 2022;13.813.
Cospain A, Schaefer E, Faoucher M, et al. Skraban-Deardorff syndrome: Six new cases of WDR26-realted disease and expansion of the clinical phenotype. Clinical Genetics. 2021;99:732-739.
Pavinato L, Trajkova S, Grosso E, et al. Expanding the clinical phenotype of the ultra-rare Skraban-Deardorff syndrome: two novel individuals with WDR26 loss-of-function variants and a literature review. Am J Med Genet. 2021;1-9.
Yanagishita T, Yamamoto-Shimojima K, Nakano S, et al. Phenotypic features of 1q41q42 microdeletion including WDR26 and FBXO28 are clinically recognizable: the first case from Japan. Brain and Development. 2019;41:452-455.
Skraban CM, Wells CF, Markose P, et al. WDR26 halopinsufficiency causes a recognizable syndrome of intellectual disability, seizures, abnormal gait, and distinctive facial features. Am J Hum Genet. 2017;101:139-148.
Cassina M, Rigon C, Casarin A, et al. FBXO28 is a critical gene of the 1q41q42 microdeletion syndrome. Am J Med Genet. A. 2015;167:1418-1420.
Au PY, Argiropoulos B, Parboosingh JS, et al. Refinement of the critical region of 1q41q42 microdeletion syndrome identifies FBXO28 as a candidate causative gene for intellectual disability and seizures. 2014;164A:411-448.
Skraban CM, Grand KL, Deardorff MA. WDR26-Related Intellectual Disability. 2019 Apr 25. In: Adam MP, Mirzaa GM, Pagon RA, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2023. Available from: https://www.ncbi.nlm.nih.gov/books/NBK540448/ Accessed August 16, 2023.
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