Lateonset Friedreich's disease: clinical features andmapping ofmutation totheFRDA locus

Twentytwo patients from 17 families withFriedreich's disease phenotype but withonsetranging fromtheagesof21to 36aredescribed. Comparison with"typical"Friedreich's diseasewithonset before20 yearsofageshowedonlya loweroccurrence ofskeletal deformities. Theperipheral andcentral neurophysiological findings, suralnervebiopsy, and theneuroradiological picturedidnot allowthedifferentiation between"late onset"and "typical" Friedreich's disease.Durationofdisease fromonsetto becomingconfined toa wheelchair was fiveyearslonger inlateonsetpatients. Sixteen patients and25healthy members fromeightfamilies weretypedwiththe chromosome9markersMLS1,MS,and GS4tightly linked totheFRDA locus. All families showedpositive lodscoreswith acombinedvalueof5*17atarecombinationfraction of0= 000.It is concluded that"lateonset"Friedreich's disease is milderthanthe"typical" formandthat itmaps tothesamelocuson chromosome9.