Partial trisomy 12q by duplication of 12q12->q21: a rare chromosome aberration
Partial trisomy 12q21->24 is extremely rare, but about 3 tens of cases are reported in the literature, and a dysmorphic pattern has already been associated to it. In most reported cases, severe congenital cardiopathy and lethality occurred within 1 year of life.
We herein report a rare “de novo” 12q1.2->q21 duplication and inversion of the entire duplicated segment. A 2-year-old girl, 1st child of healthy non-consanguineous parents, was born at 40 wks after normal pregnancy and delivery. Birth weight was 2535g, height 48cm, OFC 34cm with Apgar scores 3-10. The baby had mild hypotonia and walked at 24ms, when she was able to speak just a few words. At 2yrs2m she showed developmental delay and dysmorphic features, flattened nose, depressed nasal bridge, anteverted nostrils, short palpebral fissures, epicanthic folds, flat face, and unilateral transverse palmar crease (R). She had thoracic-lumbar scoliosis and flat feet. Her weight was 12600Kg (50th percentile), height 86cm (50th percentile), OFC 47,5cm (<50th percentile), palpebral fissure length 2cm (<3rd percentile). Cardiac and pulmonary clinical evaluation, cranial CAT-SCAN, and renal and abdominal ultrasonography were normal. G-banding (850 bands) revealed karyotype 46,XX, dup(12)(pter->p11.2::q21->q12::p11.1->qter) confirmed by FISH (probe coatasome 12 ONCOR®), characterizing a “de novo” interstitial 12q12-q21 duplication (mother and father had normal karyotypes). The cases of 12p duplication so far described have given rise to ample discussions of the clinical effect of the duplicated material. Diferent that a classic syndrome 12p duplication, has been suggested that 12q13->12q21.2 duplications are viable only in the mosaic form and that gene dosage effects of genes in this region cause embryonic lethality. Our case showed no mosaic form or lethality or morbidity. Further studies, especially molecular analyses, are necessary to better identify which genes are involved in lethality and morbidity.