ATAXIA OCULAR MOTOR APRAXIA SYNDROME - AN INVESTIGATION OF CELLULAR RADIOSENSITIVITY OF PATIENTS AND THEIR FAMILIES

Although ataxia-ocular motor apraxia (AOA) has been described as a dis ease entity mimicking ataxia telangiectasia (AT), no radiobiological s tudies have been carried out on cells from patients with AOA to find t heir possible relationship to AT. In the present study, cultured fibro blasts from three patients with AOA and their asymptomatic relatives ( parents and sibs) were, therefore, compared with those from a classica l AT homozygote, an AT heterozygote, and four healthy subjects for cel l survival after acute and chronic irradiation. While a moderately inc reased cellular sensitivity (compared to normal) was observed in two A OA patients and most of their relatives, the degree of their radiosens itivity was quite different from that of the AT homozygote after both acute and chronic irradiation. One AOA patient exhibited increased cel lular sensitivity similar to that of a classical AT homozygote up to 4 % survival level after chronic irradiation but not after acute irradia tion. A comparison of peripheral blood lymphocytes from two AOA patien ts, an AT homozygote, and two normal controls for spontaneous and (acu te) radiation induced chromosomal breaks also failed to show any simil arity between AOA and AT. These data support the notion that AOA is di fferent from classical AT, and may represent a distinct disease entity controlled by specific gene(s), or compound heterozygotes involving d ifferent AT genes promoting the manifestation of AOA characteristics.