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Bohring−Opitz Syndrome
Published in Dongyou Liu, Handbook of Tumor Syndromes, 2020
Bohring–Opitz syndrome (BOS) is a rare genetic disorder characterized by distinctive craniofacial appearance, abnormal posture, feeding difficulties, severe developmental delay and intellectual disability, failure to thrive, and early mortality (as a consequence of unexplained bradycardia, obstructive apnea, or pulmonary infections). Of about 60 BOS cases described to date, 75% are shown to contain de novo mutations in the Asxl1 gene. While germline Asxl1 mutations are linked to BOS phenotype, somatic Asxl1 mutations disrupt hematopoiesis, impair self-renewal capacity, and skew differentiation away from osteoblasts to adipocytes, leading to myeloid malignancies (particularly in the elderly) without BOS symptoms. In the absence of effective therapy, there is an obvious need to further uncover the molecular mechanisms of BOS, with the goal of developing novel countermeasures against this genetic condition.
C syndrome - what do we know and what could the future hold?
Published in Expert Opinion on Orphan Drugs, 2019
Roser Urreizti, Daniel Grinberg, Susanna Balcells
The relatively broad clinical spectrum of OCS overlaps other clinical entities and some patients initially considered as OCS have been finally re-diagnosed to other syndromes such as the Kleefstra Syndrome mentioned previously, Varady Syndrome or Kabuki syndrome [21,27,39–41]. In 1999, a new syndrome highly overlapping OCS but with a more severe outcome was delineated. This C-like syndrome or Bohring-Opitz Syndrome (BOS, MIM # 605,039) is clinically -and genetically- more homogeneous and it is mainly characterized by trigonocephaly (and microcephaly), nevus simplex (flammeus), intrauterine growth retardation (IUGR), failure to thrive, severe to profound developmental delay and characteristic fixed flexions of the elbows, wrists and metacarpophalangeal joints, known as BOS posture [42]. BOS is mainly due to mutations in the ASXL1 gene [42–44]. In near one third of the patients fitting a typical clinical BOS phenotype no mutations in ASXL1 can be detected, suggesting that it is a heterogeneous entity. In this sense, mutations in ASXL3 [45]; ASXL2 [46] and KLHL7 [47] have been identified in patients clinically overlapping BOS.