Neurocognitive variance and neurological underpinnings of the X and Y chromosomal variations


  • Andrea Gropman,

    Corresponding author
    • Division of Neurogenetics and Neurodevelopmental Pediatrics, Children's National Medical Center, 111 Michigan Avenue, Washington, DC 2001.
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    • Andrea Gropman, M.D., is an Associate Professor of Neurology and Pediatrics at the George Washington University of the Health Sciences and an attending at the Children's National Medical Center in Washington, DC. She is the Chief of the division of Neurogenetics and Neurodevelopmental Pediatrics. She is involved in clinical and molecular testing of patients with Neurogenetic conditions and her research is focused on neurological and neurodevelopmental phenotyping of genetic conditions. She also performs research using neuroimaging in children and adults with inborn errors of metabolism.

  • Carole A. Samango-Sprouse

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    • Carole Samango-Sprouse, Ed.D., is an Associate Clinical Professor of Pediatrics at the George Washington University School of Medicine and Health Sciences. She is actively involved in the clinical and developmental care of children with rare neurogenetic disorders. She is the CEO of the Neurodevelopmental Diagnostic Center providing care for children with uncommon neurogenetic disorders from all over the world. She writes extensively about the relationship between brain function, neurodevelopmental profile and neurogenetic disorder.

  • Conflict of interest: None.

  • How to Cite this Article: Gropman A, Samango-Sprouse CA. 2013. Neurocognitive variance and neurological underpinnings of the X and Y chromosomal variations. Am J Med Genet Part C Semin Med Genet 163C: 35–43.


X and Y chromosomal variations including tetrasomy and pentasomy conditions are rare and occur in 1:18,000–1:100,000 male births. The most common sex chromosome aneuploidy is 47, XXY for which there is a rich literature delineating the physical and neurobehavioral phenotype. Although the more complex chromosome aneuploidies 48, XXYY, 48, XXXY, and 49, XXXXY are often compared with 47, XXY (Klinefelter syndrome) because of shared features including tall stature and hypergonadotropic hypogonadism, there is a wider spectrum of physical and cognitive abilities that have recently been delineated. The phenotypic presentation of the boys with more severe aneuploidy shares some characteristics with 47, XXY, but there are also other unique and distinctive features. Previously unappreciated intact nonverbal skills have been demonstrated in association with severe developmental dyspraxia. MRI findings of white matter hyperintensities may underlie cognitive deficits and deserve further study. This report discusses what is known about clinical variability in the XY syndromes collectively evaluated through careful multidisciplinary clinical evaluation including the clinical and neurobehavioral aspects of these conditions. Variability in clinical and cognitive functioning may reflect skewed X inactivation, mosaicism, or epigenetic factors that warrant further investigation. © 2013 Wiley Periodicals, Inc.