Abstract
3q29 deletion syndrome is a rare disorder, causing a complex phenotype. Clinical features are variable and relatively non-specific. Our report aims to present an atypical, de novo deletion in chromosome band 3q29 in a preschool boy, first child of healthy non-consanguineous parents, presenting a particular phenotype (microcephaly, “full moon” face, flattened facial profile, large ears, auricular polyp, and dental dystrophies), motor and cognitive delay, characteristics of autism spectrum disorder and aggressive behavior. He also presented intrauterine growth restriction (birth weight 2,400 g) and a ventricular septal defect. SNP Array revealed a 962 kb copy number loss, on the chromosome 3q29 band (195519857–196482211), consistent with 3q29 microdeletion syndrome. FISH analysis using a RP11-252K11 probe confirmed the deletion in the proband, which was not present in the parents. Although the patient's deletion is relatively small, it partly overlaps the canonical 3q29 deletion (defined between TFRC and DLG1 gene) and extends upstream, associating a different facial phenotype compared to the classic 3q29 deletion, nonetheless showing a similar psychiatric disorder. This deletion is different from the canonical region, as it does not include the PAK2 and DLG1 genes, considered as candidates for causing intellectual disability. Thus, narrowing the genotype-phenotype correlation for the 3q29 band, FBX045 is suggested as a candidate gene for the neuropsychiatric phenotype.
Highlights
Rare diseases are complex pathologies that require a multidisciplinary team and a very rigorous clinical evaluation
The patient was evaluated by clinical geneticists along with a multidisciplinary team
Described initially as a 1.6 Mb deletion on THE long arm of chromosome 3 [1, 3], the 3q29 deletion syndrome was defined as a recurrent subtelomeric deletion between TFRC and DLG1 genes [6]
Summary
Rare diseases are complex pathologies that require a multidisciplinary team and a very rigorous clinical evaluation. Non-specific phenotype that makes the clinical diagnosis difficult. 3q29 deletion syndrome is a rare condition, reported in 2001 [1] and characterized by a variable clinical presentation, with mild to moderate intellectual disability, autism, gait ataxia, a chest wall deformity and additional features, including microcephaly, cleft lip and palate, horseshoe kidney and hypospadias observed in very few patients. PAK2 and DLG1 genes were considered as candidates for causing intellectual disability. The chromosome 3q29 band was identified as a risk factor for schizophrenia, autism, bipolar disorders [4], and other neuropsychiatric pathologies; the phenotype is not clearly defined [4,5,6]
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