3q29 microdeletion syndrome: clinical and molecular characterization of a new syndrome.
We report the identification of six patients with 3q29 microdeletion syndrome. The clinical phenotype is variable despite an almost identical deletion size. The phenotype includes mild-to-moderate mental retardation, with only slightly dysmorphic facial features that are similar in most patients: a long and narrow face, short philtrum, and high nasal bridge. Autism, gait ataxia, chest-wall deformity, and long and tapering fingers were noted in at least two of six patients. Additional features--including microcephaly, cleft lip and palate, horseshoe kidney and hypospadias, ligamentous laxity, recurrent middle ear infections, and abnormal pigmentation--were observed, but each feature was only found once, in a single patient. The microdeletion is approximately 1.5 Mb in length, with molecular boundaries mapping within the same or adjacent bacterial artificial chromosome (BAC) clones at either end of the deletion in all patients. The deletion encompasses 22 genes, including PAK2 and DLG1, which are autosomal homologues of two known X-linked mental retardation genes, PAK3 and DLG3. The presence of two nearly identical low-copy repeat sequences in BAC clones on each side of the deletion breakpoint suggests that nonallelic homologous recombination is the likely mechanism of disease causation in this syndrome.
Willatt
Lionel
L
Department of Medical Genetics, Addenbrooke's Hospital, University of Cambridge, Cambridge, United Kingdom.
Cox
James
J
Barber
John
J
Cabanas
Elisabet Dachs
ED
Collins
Amanda
A
Donnai
Dian
D
FitzPatrick
David R
DR
Maher
Eddy
E
Martin
Howard
H
Parnau
Josep
J
Pindar
Lesley
L
Ramsay
Jacqueline
J
Shaw-Smith
Charles
C
Sistermans
Erik A
EA
Tettenborn
Michael
M
Trump
Dorothy
D
de Vries
Bert B A
BB
Walker
Kate
K
Raymond
F Lucy
FL
D000015:Abnormalities, Multiple / Q000235:genetics*; D002648:Child; D002675:Child, Preschool; D002872:Chromosome Deletion; D002874:Chromosome Mapping; D002893:Chromosomes, Human, Pair 3; D019465:Craniofacial Abnormalities / Q000235:genetics; D005260:Female; D006801:Humans; D007223:Infant; D008607:Intellectual Disability / Q000235:genetics; D008297:Male; D010641:Phenotype; D013577:Syndrome