Abstract
BACKGROUND: Trisomy of the short arm of chromosome 9 (9p) is the fourth most common chromosomopathy. It is a partial or complete autosomal structural anomaly of the short arm of chromosome 9. It is generally caused by a reciprocal parental translocation between chromosome 9 and another autosome; spontaneous genetic alteration (de novo) is rare. It presents great phenotypic variability due to the variable size of the chromosome fragment involved. CLINICAL CASE: We present the case of a patient diagnosed with trisomy of the short arm of chromosome 9 with a karyotype with a chromosomal complement 46,XX,add(9)(p24), interpreted as an additional chromosome fragment on chromosome 9p. A microarray study was carried out, which reported that the 9p24.3-p13.1 region is found in triple dose, which corresponds to a partial trisomy 9p or Rethoré syndrome, which is a low prevalence entity, with an expressiveness and variable prognosis. In the present case, the finding of a murmur and diagnosis of pulmonary valve stenosis was the initial approach; The heart disease described in our patient has not been reported in the literature as part of the clinical picture, meaning that it was not an initial diagnostic suspicion. CONCLUSION: Despite having described an already defined phenotype, other clinical data that are not documented should be considered, and when new clinical evidence is found, report it and thereby expand the phenotype for a timely diagnosis.