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    Topic review

    Baraitser-Winter Syndrome

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    Submitted by: Catherine Yang
    (This entry belongs to Entry Collection "MedlinePlus ")

    Definition

    Baraitser-Winter syndrome is a condition that affects the development of many parts of the body, particularly the face and the brain.

    1. Introduction

    An unusual facial appearance is the most common characteristic of Baraitser-Winter syndrome. Distinctive facial features can include widely spaced eyes (hypertelorism), large eyelid openings, droopy eyelids (ptosis), high-arched eyebrows, a broad nasal bridge and tip of the nose, a long space between the nose and upper lip (philtrum), full cheeks, and a pointed chin.

    Structural brain abnormalities are also present in most people with Baraitser-Winter syndrome. These abnormalities are related to impaired neuronal migration, a process by which nerve cells (neurons) move to their proper positions in the developing brain. The most frequent brain abnormality associated with Baraitser-Winter syndrome is pachygyria, which is an area of the brain that has an abnormally smooth surface with fewer folds and grooves. Less commonly, affected individuals have lissencephaly, which is similar to pachygyria but involves the entire brain surface. These structural changes can cause mild to severe intellectual disability, developmental delay, and seizures.

    Other features of Baraitser-Winter syndrome can include short stature, ear abnormalities and hearing loss, heart defects, presence of an extra (duplicated) thumb, and abnormalities of the kidneys and urinary system. Some affected individuals have limited movement of large joints, such as the elbows and knees, which may be present at birth or develop over time. Rarely, people with Baraitser-Winter syndrome have involuntary muscle tensing (dystonia).

    2. Frequency

    Baraitser-Winter syndrome is a rare condition. Fewer than 50 cases have been reported in the medical literature.

    3. Causes

    Baraitser-Winter syndrome can result from mutations in either the ACTB or ACTG1 gene. These genes provide instructions for making proteins called beta (β)-actin and gamma (γ)-actin, respectively. These proteins are active (expressed) in cells throughout the body. They are organized into a network of fibers called the actin cytoskeleton, which makes up the cell's structural framework. The actin cytoskeleton has several critical functions, including determining cell shape and allowing cells to move.

    Mutations in the ACTB or ACTG1 gene alter the function of β-actin or γ-actin. The malfunctioning actin causes changes in the actin cytoskeleton that modify the structure and organization of cells and affect their ability to move. Because these two actin proteins are present in cells throughout the body and are involved in many cell activities, problems with their function likely impact many aspects of development, including neuronal migration. These changes underlie the variety of signs and symptoms associated with Baraitser-Winter syndrome.

    4. Inheritance

    This condition is described as autosomal dominant, which means one copy of the altered gene in each cell is sufficient to cause the disorder. The condition almost always results from new (de novo) mutations in the ACTB or ACTG1 gene and occurs in people with no history of the disorder in their family.

    5. Other Names for This Condition

    • BRWS
    • cerebro-frontofacial syndrome, type 3
    • Fryns-Aftimos syndrome
    • iris coloboma with ptosis, hypertelorism, and mental retardation

    This entry is adapted from https://medlineplus.gov/genetics/condition/baraitser-winter-syndrome

    References

    1. Baraitser M, Winter RM. Iris coloboma, ptosis, hypertelorism, and mentalretardation: a new syndrome. J Med Genet. 1988 Jan;25(1):41-3.
    2. Pallotta R. Iris coloboma, ptosis, hypertelorism, and mental retardation: anew syndrome possibly localised on chromosome 2. J Med Genet. 1991May;28(5):342-4. Review.
    3. Ramer JC, Lin AE, Dobyns WB, Winter R, Aymé S, Pallotta R, Ladda RL.Previously apparently undescribed syndrome: shallow orbits, ptosis, coloboma,trigonocephaly, gyral malformations, and mental and growth retardation. Am J Med Genet. 1995 Jul 3;57(3):403-9. Review.
    4. Rivière JB, van Bon BW, Hoischen A, Kholmanskikh SS, O'Roak BJ, Gilissen C,Gijsen S, Sullivan CT, Christian SL, Abdul-Rahman OA, Atkin JF, Chassaing N,Drouin-Garraud V, Fry AE, Fryns JP, Gripp KW, Kempers M, Kleefstra T, Mancini GM,Nowaczyk MJ, van Ravenswaaij-Arts CM, Roscioli T, Marble M, Rosenfeld JA, Siu VM,de Vries BB, Shendure J, Verloes A, Veltman JA, Brunner HG, Ross ME, Pilz DT,Dobyns WB. De novo mutations in the actin genes ACTB and ACTG1 causeBaraitser-Winter syndrome. Nat Genet. 2012 Feb 26;44(4):440-4, S1-2. doi:10.1038/ng.1091.
    5. Rossi M, Guerrini R, Dobyns WB, Andria G, Winter RM. Characterization of brainmalformations in the Baraitser-Winter syndrome and review of the literature.Neuropediatrics. 2003 Dec;34(6):287-92. Review.
    6. Verloes A. Iris coloboma, ptosis, hypertelorism, and mental retardation:Baraitser-Winter syndrome or Noonan syndrome? J Med Genet. 1993 May;30(5):425-6.
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