Case report: Partial trisomy 12p associated with 4p deletion due to patients t(12p-;4p+) translocation

The similar clinical findings noted in the case presented and the ten other reported cases of 12p trisomy have permitted the delineation of the specific abnormalities seen in this particular malformation syndrome. As outlined by Rethore, Tenconi et al and Bijlsma et al, these characteristic dysmorphic features include: high, prominent forehead; flat, round face with prominent cheeks; flat nasal bridge; short nose; large philtrum; dysplastic ears; down-turned mouth with everted lower lip; clinodactyly of the 5th finger; abnormally placed thumb and simian crease. Physical growth is normal while psychomotor development is retarded. In all 11 cases the 12p trisomy has resulted from a parental translocation; 6 paternal and 5 maternal, involving chromosome 12 and chromosomes 4, 6, 7, 8 (2 cases), 9, 14 (2 cases), and 21 (3 cases). Bijlsma has summarized the clinical and cytogenetic findings in all of the cases except that of Tenconi et al. However, the proband in this case has many dysmorphic findings other than those of the 12p trisomy syndrome. Many are identifiable as those associated with 4p monosomy (deletion) or Wolf syndrome. A deletion involving the chromosomal material from the 4p16 band to the 4p terminus results in this malformation syndrome. In addition to being trisomic for the 12p11 → 4pter segment, the proband is also monosomic for the 4p16 → 4pter segment.