[18q syndrome with deficiency of myelin basic protein (MBP)].

The Authors present a patient with 18q- Syndrome in which lymphatic cell karyotype could resume development of extrapyramidal degeneration signs before they appeared. Severity range of phenotypic manifestations in the 18q- syndrome is correlated with chromosomic breakpoint and with genetic background. Many chromosome 18's distal arm genes have been mapped Myelin Basic Protein gene (MBP) has been located in 22-23 position; it forms about 30-40% of myelinic sheath proteins. Failure in MBP gene expression would be correlated in the central white matter with extrapyramidal system degeneration signs: in 18q- patients with involuntary movements studied by MRI or by post-mortem autopsy unmyelinated areas in central white matter tracts have been put in evidence. As MBP absence in peripheral nervous system does not appear to have a functional effect, it has been suggested that some specific component of peripheral myelin is functionally equivalent to MBP and capable to substitute this protein in its absence.