Chronic Progressive External Ophthalmoplegia

S U M M A R Y — Th i s s tudy quantif ies the m a i o r e lect ron m i c r o s c o p i c changes in l imb muscle b iops ies f r o m 31 out of 34 pat ients wi th the s y n d r o m e of ch ron ic p rogress ive external oph tha lmopleg ia . Pat ients w e r e d iv ided into three cl inical g r o u p s — A ) 10 sporad ic cases wi th musc l e weakness o n l y ; B ) 9 familial cases w i t h musc le weakness o n l y ; C) 15 cases wi th musc le weakness and one o r m o r e of the fo l l owing fea tures : p igmen ta ry ret inopathy, cerebel lar ataxia, py ramida l s i gns and per ipheral neuropathy . E lec t ron mic roscop ic mi to chondr ia l abnormal i t ies w e r e found in all g r o u p s (8 pat ients f rom g r o u p A , 3 f rom g roup B, 14 f r o m g r o u p C ) . Quanti tat ive measurements of certain musc l e f ibre const i tuents , using a po in t -coun t ing technique, revealed decreased myof ib r i l vo lume-f rac t ions and increased vo lume-f rac t ions of mi tochondr ia , g l y c o g e n and l ipid in s o m e b iops i e s f rom each g roup . Mi tochondr ia l vo lume-f rac t ions cor re la ted pos i t ive ly wi th l ipid content , the p ropor t ion of type 1 f ibres , and the percen tage of f ibres w i t h increased ox ida t ive enzyme act ivi ty . The three g r o u p s def ined c l in ica l ly s h o w e d no s igni f icant d i f ferences in terms of the relative p ropor t ions of these measured const i tuents .