PSYCHIATRIC-DISORDER IN A FAMILIAL 15-18 TRANSLOCATION AND SUBLOCALIZATION OF MYELIN BASIC-PROTEIN TO 18Q22.3

Two related patients with similar clinical features consisting of a fe w dysmorphic signs and psychiatric disturbance were reported to have a partial trisomy of chromosomes 15(pter-q13.3) and 18(q23-qter) derivi ng from a familial translocation t(15;18). One patient is affected by bipolar disorder and the other by schizoaffective disorder, Both cases have a predominantly affective course; nevertheless, a clear diagnosi s is difficult in the first patient, who is 15 years of age, and only a longitudinal course will allow us to establish a definite diagnosis. The possibility that these two pathologies belong to a single categor y is discussed, and the presence of a susceptibility locus on chromoso me 18 is hypothesized. Cytogenetic data, FISH, and DNA studies indicat e that the myelin basic protein (MPB) gene is not involved in the tran slocation, and localize it centromeric to the breakpoint on chromosome 18(q22.3). Thus, it is unlikely to be involved in the disease. (C) 19 95 Wiley-Liss, Inc.