B-186 Pericentric Inversion of Chromosome 9-inv(9)(p12q13): Findings Beyond Infertility Encountered on a Retrospective Study

Background Pericentric inversion of chromosome 9, referred to as inv(9), is a frequent finding in human karyotype, ranging from 1% to 4% in the general population. Among the countless possibilities of pericentric inversions of chromosome 9, the inv(9)(p12q13) variant is the most common. Although this variant was considered a benign population variant, many studies associate the variant with infertility and spontaneous and repeated miscarriages. In the clinical laboratory practice we observed that this finding was present in patients to investigate other symptoms and clinical findings. Analyzing the genetic data obtained through Karyotyping, in a large laboratory, we showed that the inv(9)(p12q13) variant was present in patients for investigation of infertility, developmental delay, suspected syndromes, physical changes, miscarriage repetitive, mental retardation, seizures, hydrocephalus, amenorrhea, hypotelorism, family history of genetic diseases, neurofibromatosis, precocious and late puberty and tonic crises. This study aims to relate inv(9)(p12q13) to clinical findings. Methods Retrospective analysis of G-band Karyotype results performed in a large laboratory in São Paulo, Brazil from July/2010 to December/2023. We selected 168 patients with the inv(9)(p12q13) variant who were grouped by diagnostic hypothesis. Results In 39,995 karyotyped individuals, the frequency of pericentric inversion of chromosome 9 was 0.50% and the inv(9)(p12q13) variant represented 84% of 9 inversions. Based on the diagnostic hypotheses, 168 cases were classified as following: infertility (34.52 %), developmental delay (22.62%), clinical suspicion of syndromes (17.86%), physical changes (8.93%), repetitive abortions (4.76%), mental retardation (2.98%), seizures (1.19%), hydrocephalus, (0.60%) hypotelorism (0.60%), neurofibromatosis (0.60%), and 9 cases for other distinct hypothesis. We selected the group that investigated developmental delay, using the number of cases as a criterion, and carefully analyzed individual clinical information. A female patient had a previous diagnosis of Dandy Walker, a syndrome clinically characterized by moderate delay in psychomotor development, mental retardation, microcephaly, seizures, hypotonia and hydrocephalus. She was diagnosed by imaging tests, such as head computed tomography and magnetic resonance imaging. Neuroradiological findings were characteristic, such as cystic dilation of the fourth ventricle and changes in the cerebellar vermis. Conclusions Although pericentric inversion of chromosome 9- inv(9)(p12q13) is well described in cases of infertility investigation, our results demonstrated a high frequency of other clinical conditions. In special, one patient had a confirmed diagnosis of Dandy Walker Syndrome. Further studies are necessary to understand the role of this inversion on other clinical presentations, malformations and anomalies, including cases resembling phenotypic characteristics of Dandy Walker disease.