The article brings to light the very first case of trisomy 20p resulting from a maternal pericentric inversion in a 2 1/2-year old boy. The study outlines the characteristic clinical features of the syndrome, i.e. round face, upslanting palpebral fissures, microretrognathia, normal growth, slight psycho-motor retardation and congenital heart defects. The association of the der(20) inv(20) (p112q133) mat and brachymesophalangy of index ("Mohr-Wriedt" type of brachydactyly) enables the authors to suggest that chromosome 20 may be held responsible for this particular malformation.