Trisomy of the short arm of chromosome 5 due to a de novo inversion and duplication (5)(p15.3 p13.3)

Partial trisomies of the short arm of chromosome 5 are uncommon. The first description was made by Lejeune et al., in 1964. It has been suggested that the critical region for 5p trisomy syndrome lies between 5p10 and 5p13. We report on a Mexican girl who developed severe mental retardation and generalized tonic clonic seizures at age 1 year. On physical examination at age 5 years, she had macrodolichocephaly, upslanted palpebral fissures, bilateral inner epicanthic folds, low nasal root, and malformed ears with posterior rotation which are clinical characteristics of 5p trisomy syndrome. The cytogenetic study with G bands and FISH with painting for chromosome 5 and with the cri-du-chat 5p15 unique sequence probe showed a duplication and inversion of 5p [46,XX, dup(5)(p15.3 p13.3)] which overlaps with the critical region for 5p trisomy syndrome. Our patient shares clinical characteristics with the patients described in the literature with involvement of this critical region. Both parents have normal karyotypes indicating the rearrangement is de novo. Only one patient has been reported in the literature with the same cytogenetic rearrangement as our patient, but this patient had a different phenotype. Since they only performed conventional cytogenetics and we performed FISH to confirm the diagnosis, the differences in the phenotypes could be explained by the presence of other genes involved in the rearrangement. The combined use of conventional and molecular cytogenetics in this case allows a more precise diagnosis and furthers knowledge in phenotype/genotype correlation. © 2005 Wiley-Liss, Inc.