Introduction: Trisomy 9 is an uncommon chromosome abnormality that may be seen in a mosaic or non-mosaic state.
Objective: To better define the phenotype and prognosis of this disorder we report a new case of mosaic trisomy 9 with a long-term survival.
Clinical report: We present the case of a female patient, born from the first pregnancy of a healthy couple. Fetal ultrasounds disclosed intrauterine growth retardation and oligohydramnios. Cesarean section was performed in the 34th week. Birth weight was 1,478 g. Neonatal examination showed: dolichocephaly; hypotelorism, microphthalmia, short palpebral fissures; broad-based nose with bulbous tip; micrognathia; low-set malformed ears; abnormal hands and feet; no other malformations. The initial karyotype determination was normal (46,XX). At 17 months of age, a second karyotype was requested because the patient developed severe psychomotor retardation. Chromosome analysis showed mosaic trisomy 9 (46,XX/47,XX, + 9). Six months later, a single upper central incisor was noted. To our knowledge, this feature has not been reported previously in the trisomy 9. The patient is now 4 years old. She shows severe psychomotor retardation, but no other complications.
Comments: It is important to be aware of the possibility that mosaicism may exist in a patient with normal blood karyotype and abnormal phenotype. We conclude that a great number of cells is needed in order to obtain a correct karyotype diagnosis. Correct diagnosis is essential to define the prognosis and provide accurate genetic counselling.