Background. 3q29 microdeletion syndrome (OMIM 609425), first described in 2005, is a rare copy number variation (CNV), accompanied by various neurodevelopmental and psychiatric problems. Phenotypic features of the syndrome have not been fully characterized due to the new definition and rarity. Facial dysmorphology, musculoskeletal anomalies, cardiovascular abnormalities, gastrointestinal abnormalities, and dental abnormalities can be seen.

Case. A 28-month-old male patient was brought to the child and adolescent psychiatry clinic with a complaint of speech delay. He had mild dysmorphic symptoms. He was also sensitive to voice and often covered his ears. Balloon valvuloplasty was performed on the postnatal 28th day due to severe pulmonary stenosis. While karyotype was found to be normal, in array-Comparative genomic hybridization (aCGH), copy loss was detected in the long arm of chromosome 3 (arr[hg19] 3q29[196,209,689-197,601,344]x1), which contains approximately 1.4 Mb harboring 30 genes. Genetic counseling was given to the family of the patient who was diagnosed with 3q29 microdeletion syndrome.

Conclusions. In conclusion, we present 3q29 microdeletion syndrome with global developmental delay (GDD), dysmorphic face, hyperacusis, scoliosis, and severe pulmonary stenosis. Performing genetic analysis in patients with developmental delay and congenital heart disease (CHD) for which the cause cannot be explained will prevent these rare diseases from being missed, and the characteristics of the diseases will be better characterized with the reported cases.

Keywords: 3q29 microdeletion syndrome, aCGH, cardiac defects, child, developmental delay