Tetrasomy 9p: case report of an infant with favorable outcome

Abstract

Introduction: Tetrasomy 9p occurs due to the presence of an isochromosome derived from the short arm of chromosome 9, evidencing a wide range of phenotypic manifestations ranging from craniofacial malformations to incompatibility with life. Objective: To describe an infant with tetrasomy 9p without mosaicism and a favorable clinical evolution despite complications during hospitalization, to add this disease to the list of differential syndromic diagnoses to be considered by the pediatrician. Case description: This is a 7-month-old infant, born to a 32-year-old non-consanguineous couple. During prenatal care, abnormalities were identified on morphological ultrasound, which at birth presented as brachycephaly, ocular hypertelorism, high nasal root (Greek warrior helmet), bilateral preauricular skin tag, blepharophimosis, bilateral cleft lip and palate, atypical genitalia with bilateral cryptorchidism and hypoplasia of the scrotum (Prader 4), ostium secundum-type atrial septal defect (ASD) with hemodynamic repercussions, as well as supratentorial ventricular asymmetry on neuroimaging. The karyotype showed [47, XY, +i(9)(p10)]. Despite multiple complications during prolonged hospitalization, the patient was discharged after 5 months. Discussion: Although it is a rare chromosomal disorder, tetrasomy 9p should be considered by the pediatrician as a differential diagnosis, as its spectrum of presentation is polymorphic and similar to that of other phenotypes of chromosomal anomalies. Despite the unfavorable prognosis, it is possible to de-hospitalize these patients, and the attending physician should be prepared to continue the outpatient follow-up in conjunction with the multidisciplinary team.