Abstract
Blood lymphocytes from six unrelated patients with neurofibromatosis and three normal controls were examined for their response to different doses (0, 75, 150, 300, 400 rad) of x‐radiation, as measured by chromosome aberrations (gaps, breaks, dicentrics, centric rings, acentric ring, fragments, and minutes). Cytogenetic studies on phytohemagglutinin‐stimulated cells revealed chromosomal instability in the neurofibromatosis lymphocytes as shown by the significant increase in the incidence of gaps, breaks and dicentrics. This increase paralleled the increase in the dose of irradiation. The significance of these findings is discussed.