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Review
. 2020 Aug;22(8):1338-1347.
doi: 10.1038/s41436-020-0811-8. Epub 2020 May 19.

Further delineation of the clinical spectrum of KAT6B disorders and allelic series of pathogenic variants

Li Xin Zhang #  1 Gabrielle Lemire #  2 Claudia Gonzaga-Jauregui  3 Sirinart Molidperee  1 Carolina Galaz-Montoya  3 David S Liu  3 Alain Verloes  4 Amelle G Shillington  5 Kosuke Izumi  6 Alyssa L Ritter  7 Beth Keena  6 Elaine Zackai  7   8 Dong Li  9 Elizabeth Bhoj  7 Jennifer M Tarpinian  10 Emma Bedoukian  10 Mary K Kukolich  11 A Micheil Innes  12 Grace U Ediae  13 Sarah L Sawyer  14 Karippoth Mohandas Nair  15 Para Chottil Soumya  15 Kinattinkara R Subbaraman  15 Frank J Probst  3   16 Jennifer A Bassetti  3   16 Reid V Sutton  3   16 Richard A Gibbs  3 Chester Brown  17 Philip M Boone  18 Ingrid A Holm  18 Marco Tartaglia  19 Giovanni Battista Ferrero  20 Marcello Niceta  19 Maria Lisa Dentici  19 Francesca Clementina Radio  19 Boris Keren  21 Constance F Wells  22 Christine Coubes  22 Annie Laquerrière  23 Jacqueline Aziza  24 Charlotte Dubucs  24 Sheela Nampoothiri  25 David Mowat  26 Millan S Patel  27 Ana Bracho  28 Francisco Cammarata-Scalisi  29 Alper Gezdirici  30 Alberto Fernandez-Jaen  31 Natalie Hauser  32 Yuri A Zarate  33 Katherine A Bosanko  33 Klaus Dieterich  34 John C Carey  35 Jessica X Chong  36   37 Deborah A Nickerson  37   38 Michael J Bamshad  36   37 Brendan H Lee  3 Xiang-Jiao Yang  39 James R Lupski  3   16 Philippe M Campeau  40
Affiliations
Review

Further delineation of the clinical spectrum of KAT6B disorders and allelic series of pathogenic variants

Li Xin Zhang et al. Genet Med. 2020 Aug.

Abstract

Purpose: Genitopatellar syndrome and Say-Barber-Biesecker-Young-Simpson syndrome are caused by variants in the KAT6B gene and are part of a broad clinical spectrum called KAT6B disorders, whose variable expressivity is increasingly being recognized.

Methods: We herein present the phenotypes of 32 previously unreported individuals with a molecularly confirmed diagnosis of a KAT6B disorder, report 24 new pathogenic KAT6B variants, and review phenotypic information available on all published individuals with this condition. We also suggest a classification of clinical subtypes within the KAT6B disorder spectrum.

Results: We demonstrate that cerebral anomalies, optic nerve hypoplasia, neurobehavioral difficulties, and distal limb anomalies other than long thumbs and great toes, such as polydactyly, are more frequently observed than initially reported. Intestinal malrotation and its serious consequences can be present in affected individuals. Additionally, we identified four children with Pierre Robin sequence, four individuals who had increased nuchal translucency/cystic hygroma prenatally, and two fetuses with severe renal anomalies leading to renal failure. We also report an individual in which a pathogenic variant was inherited from a mildly affected parent.

Conclusion: Our work provides a comprehensive review and expansion of the genotypic and phenotypic spectrum of KAT6B disorders that will assist clinicians in the assessment, counseling, and management of affected individuals.

Keywords: KAT6B; KAT6B disorders; SBBYSS; Say–Barber–Biesecker–Young–Simpson syndrome; genitopatellar syndrome.

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Conflict of interest statement

CONFLICT OF INTEREST

Baylor College of Medicine (BCM) and Miraca Holdings have formed a joint venture with shared ownership and governance of Baylor Genetics (BG), which performs clinical microarray analysis and clinical exome sequencing. J.R.L. serves on the Scientific Advisory Board of BG. J.R.L. has stock ownership in 23andMe, is a paid consultant for Regeneron Pharmaceuticals, and is a coinventor on multiple United States and European patents related to molecular diagnostics for inherited neuropathies, eye diseases, and bacterial genomic fingerprinting. The Department of Molecular and Human Genetics at Baylor College of Medicine derives revenue from molecular genetic testing offered in the Baylor Genetics Laboratories.

Figures

Figure 1:
Figure 1:
Clinical photographs of 20 newly reported individuals with KAT6B disorders (GPS: Genitopatellar Syndrome/SBBYSS: Say-Barber-Biesecker-Young-Simpson Syndrome/ NOS: not otherwise specified) showing: a) Facial features of affected individuals. Note the blepharophimosis, ptosis and mask-like facies in individuals with SBBYSS and the intermediate phenotype. b) Long thumbs and/or long great toes (upper left: individual 13; upper right: individual 15; lower left and lower right: individual 29). c) Flexion contractures and club feet (left: individual 24; right: individual 5). d) Absent patella in individual 5. e) Pre-axial polydactyly of the right hand in individual 25. f) Overlapping toes in individual 21. g) A newborn with GPS who died after birth at 28 weeks of gestation (Individual 8). Note the high forehead, blepharophimosis, small palpebral fissures with hypertelorism, sparse eyebrows and eyelashes, small simplified ears with bilateral pits, proximal/distal arthrogryposis and contractures of the hip/knees.
Figure 1:
Figure 1:
Clinical photographs of 20 newly reported individuals with KAT6B disorders (GPS: Genitopatellar Syndrome/SBBYSS: Say-Barber-Biesecker-Young-Simpson Syndrome/ NOS: not otherwise specified) showing: a) Facial features of affected individuals. Note the blepharophimosis, ptosis and mask-like facies in individuals with SBBYSS and the intermediate phenotype. b) Long thumbs and/or long great toes (upper left: individual 13; upper right: individual 15; lower left and lower right: individual 29). c) Flexion contractures and club feet (left: individual 24; right: individual 5). d) Absent patella in individual 5. e) Pre-axial polydactyly of the right hand in individual 25. f) Overlapping toes in individual 21. g) A newborn with GPS who died after birth at 28 weeks of gestation (Individual 8). Note the high forehead, blepharophimosis, small palpebral fissures with hypertelorism, sparse eyebrows and eyelashes, small simplified ears with bilateral pits, proximal/distal arthrogryposis and contractures of the hip/knees.
Figure 2:
Figure 2:
Distribution of all pathogenic variants in KAT6B reported in literature (upper panel) and 23 new variants reported in this article (lower panel) with the associated phenotype(s). GPS: Genitopatellar Syndrome/SSBYSS: Say-Barber-Biesecker-Young-Simpson Syndrome. NOS: not otherwise specified. The variant c.5624_5625del/p.Ala1876Leufs*3 reported by Gannon et al in 2015 has not been included in this figure, because of discordance between the reported cDNA and protein change.

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