RESUMEN
While duplication and deletion of the short arm of chromosome 12 cause well-recognized syndromes, duplication of the long arm chromosome 12 is rarely observe. We are reporting a duplication of chromosome 12 distal to band q24.1 in a five-month-old child. His chromosome constitution is 46,XY,-4+der(4),t(4:12)(p16;q24.1)mat. The balanced translocation is also carried by his maternal grandmother and two of the mother's brothers. The malformation syndrome consisted of unusual facial appearance and anomalies of the musculoskeletal, cardiovascular, genitourinary, and central nervous systems. Four previously reported patients had similar break points on chromosome 12 with similar malformations; therefore, phenotype-karyotype correlation suggests a definitive malformation syndrome associated with duplication of chromosome region 12q24.1 leads to qter.