A pericentric inversion, 5p–q+, and additional complex rearrangements in a case of cri-du-chat syndrome

A malformed girl presenting the typical clinical features of the cri-du-chat syndrome is described. Her karyotype contains three grossly abnormal chromosomes, a 5p–q+, a ring C and a 15q+. Formally, a minimum of six breaks is involved in the origin of this complex anomaly. Based on autoradiographic evidence, it is concluded that the cri-du-chat phenotype in this patient is due to a submicroscopical lesion in the distal segment of the short arm of the abnormal No. 5 chromosome; without noticeable loss of chromatin, a break involved in a pericentric inversion, 5p–q+ seems to have altered a chromosome section of crucial importance. Such an interpretation is supported by the reports of cri-du-chat cases with morphologically normal No. 5 chromosomes. The additional structural rearrangements in the child’s karyotype apparently did not affect his phenotype. Blood cultures from the child’s mother showed acentric fragments and ring chromosomes in 5.3% of 225 analyzed cells. Possible causes for this high aberration rate are discussed.