Journal ofNeurology, Neurosurgery, and Psychiatry 1990;53:649-655

Vesicular changes in the myopathies of AIDS.

Ultrastructural observations and their relationshipto zidovudine treatment

Peter K Panegyres, John M Papadimitriou, Peter N Hollingsworth, John A Armstrong,Byron A Kakulas

AbstractSix patients with AIDS and AIDS relatedcomplex (ARC) who developed neuro-muscular symptoms associated withvesicular changes in muscle fibres arereported. Two patients in the advancedstages of AIDS, who did not receivezidovudine, developed proximal limbweakness and wasting: both had anecrotising myopathy with an unusualsegmental vesicular change of myo-fibres. There were numerous vesicles 0-1to 2 tm in diameter produced by dilata-tions of the sarcoplasmic reticulum infibres depleted of myofibrils. Fourpatients developed a myopathy whilereceiving zidovudine for AIDS. One ofthese had an inflammatory myopathywhich showed the development ofvesicular change due to enlargement andelectron lucency of mitochondria. Thethree other patients with ARC developedmuscle pains or weakness and elevatedserum CK while on zidovudine. Thesepatients also showed vesicular changesdue to enlargement and electron lucencyof mitochondria associated with disrup-tion of sarcomeres and the presence ofcytoplasmic bodies. The muscular symp-toms resolved when zidovudine wasstopped and repeat biopsy in one caserevealed no abnormalities.

Central and peripheral nervous system com-plications are features of the acquired immunedeficiency syndrome (AIDS).'2 Disorders ofvoluntary muscle have also been described.Among these, inflammatory myopathy,3 4inflammatory myopathy with giant cells,5necrotising myopathy with minimal inflam-matory infiltrate,6 7 myopathy with rodbodies,89 and type 2 fibre atrophy'01' havebeen recorded. Recently we described twoAIDS patients who had myopathy character-ised by vesicular changes by light micro-scopy-a rather unique myopathic reactionwhich occurred in the absence of zidovudinetreatment.'2 In this study we present theultrastructural findings of these two patientsand four other AIDS patients who alsodeveloped vesicular changes in skeletal musclewhile receiving zidovudine.

Materials and methodsSkeletal muscle for study from the right

biceps brachii and quadriceps femoris wasderived by local incision within 30 minutesafter the death of patients 1 and 2 (see below).Permission for a general necropsy was refusedin both. Muscle specimens were processed forparaffin embedded blocks, and formalin fixedfrozen sections for ORO and PAS stains.Fibre typing was performed on paraffin sec-tions using a monoclonal antibody to fastmyosin (ICN products). The paraffin-embed-ded blocks were stained with haematoxylin-eosin, picro-mallory, Fite-Faraco, Methan-amine silver, Giemsa, Gram, and Ziehl-Neel-sen stains.For electron microscopy the samples were

fixed in 2 5% gluteraldehyde in phosphatebuffer (pH 7A4) for 16 hours. They were post-fixed in 1% osmium tetroxide in phosphatebuffer for one hour, then embedded in aral-dite. Sections were cut on an LKBultramicrotome, stained with lead citrate andexamined on a Philips 410 electron micro-scope. Normal control muscles and fromHIV-Seronegative cachectic patients werecollected under similar conditions andprepared in the same way. The muscle tissuewas obtained by needled biopsy from vastuslateralis in patients 3 to 6 and processedimmediately. The staining methods fibre typ-ing and electron microscopy were performedas described above.

Case histories and pathological findingsCase 1A 23 year old bisexual male, had a past historyof rheumatic fever, psoriasis, and venerealwarts. In November 1984 he developed leth-argy, malaise, weight loss, and axillary lym-phadenopathy. He was human immunedeficiency virus (HIV) antibody positive byenzyme linked immunoabsorbent assay(ELISA). He developed oral candidiasiswhich was treated with nystatin. In Septem-ber 1985 he suffered Pneumocystis cariniipneumonia which responded to intravenousSeptrin. Ketoconazole was added to nystatinfor the treatment of severe oral candidiasis.While an inpatient he developed Giardia lam-blia enteritis which resolved with metroni-dazole. Multiple "cotton wool" spots werepresent in both retinae without papilloedema.These changes were ascribed to AIDSretinopathy. Cytomegalovirus serology andviral urine cultures were negative. The CD4count was 240 x 109/1 (ratio CD4/CD8 03-0-4). In December 1985 he was investigated

Royal Perth Hospital,Perth, Department ofNeuropathologyP K PanegyresDepartment ofClinical ImmunologyP N HollingsworthDepartment ofPathology (ElectronMicroscopy Unit)J A ArmstrongUniversity of WesternAustralia, Perth,Department ofPathologyJ M PapadimitriouAustralianNeuromuscularResearch Institute,Perth, WesternAustraliaB A KakulasCorrespondence to:Professor Kakulas,Department ofNeuropathology, RoyalPerth Hospital, Box X 2213GPO, Perth, WesternAustralia, 6001Received 31 January 1989and in revised form 15November 1989.Accepted 29 November 1989

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Figure I A myofibrewith vesicular changeassociated with internalnuclei. Arrows indicatesome vesicles.(H & E x 1624)

for headache. Neurological examination was

normal and his weight was 62 kg. A cerebralCT scan was normal. A lumbar punctureshowed clear CSF with two white cells/microlitre, 315 red cells/microlitre, protein0-31 g/l, glucose 3-4 mmol/l, and negativecryptococcal antigen. CSF cultures were

negative.Lymph node biopsy in January 1986

revealed follicular involution and Langerhansand monocytoid cell infiltrates, a patterntypical of the lymphoid depletion stage ofHIV related lymphadenopathy. Pneumocystiscarinii pneumonia recurred in May 1986 andit again responded to intravenous Septrin. InJune 1986 he was febrile and his weight had

Figure 2 A myofibreshowing numerousmembrane bound vesicles,loss of sarcomeres,remnants ofZ bands,central nuclei, andlipofuscin pigment(EM x 9100). Inset:High magnification of atriad showing the dilatedlateral sacs(EM x 35000).

dropped to 59 kg. Acyclovir was introducedand after 12 hours he was afebrile. In August1986 Mycobacterium intracellulare was isolatedfrom his faeces. His weight was now 49 kg. InDecember 1986 he developed diarrhoea andimmobility. He had received isoniazid, etham-butol, clofazamine and ansamycin over thepreceding three weeks. He was now cachectic,weighing 37 4 kg. There was proximal mus-cular weakness disproportionate to hiscachexia. Muscle power was 3/5 in theproximal shoulder and pelvic girdles. Neckflexors were 2/5 and neck extensors 3/5. Thespleen was enlarged. The haemoglobin was27 g/l and he was transfused. The creatinekinase was 20 units/l (normal < 200). Hiscondition deteriorated and he died on 7 Jan-uary 1987. He did not receive zidovudine.

Light MicroscopyThe right biceps and quadriceps muscles weresampled. Both showed excessive variation infibre size with small angulated fibres of bothhistochemical fibre types. There was no fibretype grouping in the right biceps, 58% offibres were type 2 and 42°() type 1. The mean(SD) type 2 fibre size was 15 (3) ,um and type1 29 (7) pm. The right quadriceps alsoshowed no fibre type grouping. In this muscle420O of fibres were type 2 and 58%/ type 1.The mean (SD) type 2 fibre size was 24(12),um and type 1 33 (10) gm. There wasfibre splitting, segmental necrosis, myo-phagia, and regeneration in both muscles witha slight mononuclear infiltrate. There werelong chains of central nuclei (<10) in somefibres with prominent nucleoli. Some fibreswere split. The fat, glycogen and connectivetissue contents were normal. Stains for fungiand atypical mycobacteria were negative. Fiveto 10%,O of myofibres showed a segmentalvesicular change in non-necrotic non-regen-erating fibres (fig 1). The vesicles which didnot contain fat or glycogen measured 0-25-2 jgm in diameter and were clear pink inH & E stained sections.

Electron MicroscopyElectron microscopy (EM) showed thevesicular change corresponded to aggregates ofdilated cisternae-of the sarcoplasmic reticulum(fig 2). This was associated with myofibrillardepletion disintegration of sarcomeres, andcentrally located nuclei. Some myofibresshowed an almost complete loss of theirmyofibrillar apparatus while the centrallyaggregated nuclei were characterised by muchheterochromatin which had separated from thesurrounding nuclear envelope. The mitochon-dria were generally within normal limits.Associated satellite cells were intact andapparently unaffected. No retroviral or othervirus particles were found in the muscle tissuebut typical cytoplasmic tubuloreticularinclusions were prominent in endothelial cellsand in some lymphocytes.

Case 2A 27 year old homosexual male had beenadmitted to a country hospital on the 31

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October 1986 because of intermittentabdominal pain, perianal ulceration, lymph-adenopathy, and a cutaneous eruption of bothaxillae of three weeks duration. The abdominalpain resolved spontaneously. On 1 January1987 he developed diarrhoea and had lost 20 kgin weight. Examination showed a cachecticmale with seborrhoeic dermatitis over the faceand axilla. He weighed 52 kg. Discrete lymphnodes measured 0-5 cm in diameter were pal-pable in the axillae and inguinal regions. Therewere multiple painful perianal ulcers. HIVantibody was detected by ELISA and WesternBlot. The CD4 count was 50 x 109/1, CD4/CD8 ratio 0-1. Rectal biopsy revealedintramucosal cryptosporidiosis which was alsodemonstrated by gastric aspiration. Herpessimplex type 2 was demonstrated in a perianalulcer. On the 11 February 1987 ketoconzazoleand nystatin were started for severe oeso-

phageal candidiasis. On the 17 February 1987he developed fever and neck stiffness. Lumbarpuncture showed clear CSF with no red cellsand seven white cells per microlitre. The CSFprotein was 0-36 g/l and glucose 3-7 mmol/l.Cryptococcus neoformans was cultured from theCSF. He was started on amphotericin. Hedeveloped right lower lobe pneumonia. Stap-hylococcus aureas and Haemophilus influenzaewere cultured from the sputum. Amoxycillinwas added to the treatment regime. About thistime he showed progressive immobility andweakness disproportionate to his physicaldeterioration. Muscle wasting was generalisedbut more pronounced in the proximal upperand lower limb groups. Muscle strength was 4/5 for neck flexor, shoulder and pelvic girdlegroups. Distal muscle power was normal. Theserum creatine kinase was 160 ul (NL 200). Hiscondition progressively deteriorated and deathoccurred on the 6 March 1987. He did notreceive zidovudine.

Light MicroscopyThe right quadriceps muscle showed atrophicfibres ofboth histochemical fibre types withoutgrouping. There were 26% type 2 fibres and74% type 1 fibres. The mean (SD) type 2 fibresize was 25 (8) gm and type 1 26 (12) ym. Therewas occasional segmental necrosis ofmyofibreswith myophagia. The fat, glycogen and con-

nective tissue content was normal. There was

minimal mononuclear inflammatory infiltrate.Approximately 20% of non-necrotic fibresshowed segmental vesicular change character-ised by numerous pink-clear vesicles by H & Emeasuring 05-1 gm in diameter and replacingthe normal myofibrillary architecture. Thischange was associated with central nuclei. Thevesicles did not contain fat or glycogen andwere visible in both paraffin and frozen sec-

tions.

Electron Microscopy

The vesicles corresponded to dilatations of theterminal cisternae of the sarcoplasmicreticulum. The majority of vesicles contained a

mildly osmophilic material but several were

electron lucent. Some vesicles were adjacent tothe T-tubules and were obviously dilated

lateral Eacs. Disruption of the myofilamentousarchitecture was found in association withthese vesicles. Some mitochondria wereswollen but were easily distinguishable fromthe dilated sarcoplasmic reticulum. Occasionalmyeloid bodies were identified. Many nucleiexhibited peripheral clumping of chromatinand prominent nucleoli. The fat and glycogencontent was within normal limits. Atrophicfibres showed excessive folding of the sar-colemma and coalescence of nuclear mem-branes between dark shrunken nuclei. Virusparticles were not identified.

Case 3This was a 34 year old male homosexual with ahistory of perianal herpes. In June 1986 HIVantibodies were detected by the ELISA assaywhile he was asymptomatic. In August 1986 hedeveloped generalised lymphadenopathy andCD4 count 280 x 109/1, CD4/CD8 ratio 0.2-0-3. He had Pneumocystis carinii pneumonia inJuly 1987 which responded to intravenousSeptrin. He was thereafter maintained on Fan-sidar (sulphadoxine and pyrimethamine).Zidovudine 1200 mg daily was introduced inSeptember, 1987. Atypical mycobacteria wereisolated from bronchial washings in October1987 and isoniazid, rifampicin, and pyridoxinewere started. Anti-tuberculous treatment waswithdrawn in December 1987. In February1988 he developed progressive muscular weak-ness. On examination there was generalisedmuscle wasting and weakness, most marked inthe neck and proximal limb muscles. Hisweight was 62-9 kg. The creatine kinase was468 u/l (normal < 200). He developed dys-phagia due to candida in March 1988. He wasstarted on ketaconazole but this was changed toamphotericin lozenges after one month. Hismuscular weakness persisted and in April 1988the CK was 773 u/l. The zidovudine wasstopped in April after a muscle biopsy showedan inflammatory myopathy (described below).His muscular weakness further progressedwith difficulty in walking. In July 1988 hisweight was 59 3 kg and CK was 740 u/l. Asecond muscle biopsy was performed.Zidovudine was reintroduced in August 1988and there was slight improvement in his musclepower. From September to December 1988 hismuscle power deteriorated. The CK was now1178 u/1. His weight was 50 kg and a thirdmuscle biopsy was performed.

Light MicroscopyThe first biopsy of the right vastus lateralisperformed in April 1988 showed a polyfocalmononuclear infiltrate with necrosis, myo-phagia and regeneration. Some small angulatedfibres were found. There were 57% type 2fibres and 43% type 1 fibres. The mean (SD)type 2 fibre diameter was 43 (11) gm and fortype 1 fibres 54 (11) gm. The second biopsywas from the left vastus lateralis taken in July1988. It also showed a polyfocal mononuclearinfiltrate with myophagia and regeneration.Split fibres and some small angulated fibreswere present. There were 42% type 2 fibresand 58% type 1 fibres. The mean (SD) type 2

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fibre diameter was 19 (6) gm and type 1 24(5) gm. Approximately 5% of non-regener-ating, non-necrotic fibres showed segmentalvesicular change characterised by pink-clearvesicles by H & E ranging in size from 0-2 to1 gm. This change was not found on review ofthe first biopsy. Microvesicular changereplaced the normal myofibrillary architecturein many fibres. The vesicles did not contain fator glycogen. The third muscle biopsy inDecember 1988 showed persistence of theinflammatory myopathy and the micro-vesicular degeneration was more fullydeveloped affecting 10-20% of fibres (fig 3).

Figure 4 Case 3: portionof a myofibre displayingseveral enlargedmitochondria. Note theincreased number of cristaemitochondriales,vesiculation and presenceof electron dense bodies onthe inner chamber(EM x 28000). Inset:Mitochondrion showing awhorled arrangement of itscristae (EM x 24000).

There were 39% type 2 fibres and 61% type 1.The mean (SD) type 2 fibre diameter was 16(10) gm and type 1 30 (8) pm.

Electron MicroscopyUltrastructure of the first biopsy showed a

patchy loss of myofibrils with irregularities ofZ and I bands. Several cytoplasmic bodies wereidentified adjacent to aggregates of swollenmitochondria. The muscle nuclei, sarcolemma,and sarcoplasmic reticulum were normal. Virusparticles were not found. The second biopsyshowed in several fibres the accumulation ofabnormal enlarged (5-7 jm) mitochondriawhich possessed numerous cristae which on

occasions were concentrically arranged. Inaddition myofibrillary disorganisation andincrease in the number of lipid globules werealso seen in such fibres. Many mitochondria ofnear normal size had distorted cristae, vesiclesand electron dense deposits in their innerchamber (fig 4). Other myofibres showedminicores, cytoplasmic bodies, and excess lipidglobules. The sarcoplasmic reticulum was

normal. The third biopsy showed similar mito-chondrial abnormalities associated withmyofibrillary disorganisation, cytoplasmicbodies, and Z band streaming.

Case 4A 52 year old male homosexual, HIV antibodypositive by ELISA and Western blot since1982. He developed generalised lymphadeno-pathy in 1984 and lymph node biopsy showedfollicular hyperplasia with HIV-typeretrovirus particles demonstrated ultrastruc-turally in the expanded dendritic cell labyrin-ths. His CD4 count was 320 x l09/l and CD4/CD8 ratio was 0 5. Zidovudine 1-2 g/day wasstarted February 1988. He has received no

other medications. Over the four monthsbefore November 1988 he experienced "achesand stiffness" in his thighs and legs whenstanding from a low chair and walking. His CKin January 1988 was 193 u/l (NL 200) and hisweight 87-2 kg. In September 1988 the CK was

448 u/l and body weight 88 kg. The zidovudinewas ceased in November 1988. After two weeksthere was improvement in the thigh symptoms.After four weeks he was asymptomatic with a

normal CK (170 u/l).

Light MicroscopyMuscle biopsy in November 1988 of the vastuslateralis showed slight variation in fibre sizewith occasional small angulated fibres. Lessthan 5% of fibres showed vesicular changeassociated with central nuclei. These vesiclesmeasured approximately 1 pm in diameter anddid not contain fat or glycogen. There was no

necrosis, inflammation or group atrophy.There were 78% type 1 fibres and 22% type 2.The mean (SD) fibre diameter of type 1 fibreswas 37 (6) jm and type 2 36 (13) jim. Repeatbiopsy in January 1988 was normal.

Electron MicroscopyIn a minority of fibres, mitochondria were

enlarged and showed increased numbers of

Figure 3 Three myofibreswith vesicular changes ofsarcoplasm and loss ofstriations are shown at theright of thefigure. Normalmyofibres are also seen(S). (H& E x 691).

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cristae, some of which were arranged in whorlsor networks rather than the usual parallel array.The sarcomeres and nuclei were normal. Noviral particles were identified. Mitochondriawere normal in the repeat biopsy.

Case SA 50 year old homosexual male with AIDSrelated complex since 1986. His CD4 count was350 x 109/1 and CD4/CD8 ratio 0-1 and anti-HIV antibody positive by ELISA and Westernblotting. He had syphilis treated with penicillinin 1974 and urogenital herpes in 1984. He hadbeen on zidovudine 1-2 g/d for 12 months andFansidar for two years. In the three monthsbefore October 1988 he had lost approximately7 kg in weight and for two months complainedof muscle "pains" in the thighs. He haddifficulty climbing stairs. The CK was 544 u/lin August 1988 and was 930 u/l in September1988 (NL 200). In October 1988 slight wastingwith tenderness of the quadriceps was noted.There was also wasting of the sternomastoidswith neck flexion being 4/5. Following with-drawal of zidovudine in October 1988 herecovered from his muscular weakness and byDecember 1988 the CK fell to 140 u/l.

Light MicroscopyA biopsy from vastus lateralis showed slightvariation in fibre size with internal nuclei inabout 10% of fibres. Necrosis and myophagiawere present. About 5% of fibres showedvesicles measuring 0 5-1 pm in diameter. Theywere pink-clear by H & E and replaced thenormal constituents. Eosinophilic intracylo-plasmic inclusions were found in occasionalfibres. There were 59% type 2 fibres and 41%type 1. The mean (SD) fibre diameter of type 2fibres was 18 (5) gm and 27 (8) um for type 1.

Electron MicroscopyMany fibres showed derangement ofmyofilaments, enlarged mitochondria (1 to7 Mm), cytoplasmic bodies, and central nucleiwith prominent nucleoli. The mitochondriashowed increased numbers of cristae, many ofwhich lacked the normal pattern of parallelorganisation, whilst others were arranged inconcentric "whorls". In a few electron densebodies were seen within the inner chamber.

Case 6A 46 year old merchant seaman contractedHIVinfection after a blood transfusion in July 1987.Three months later he developed fever andlymphadenopathy. He was HIV antibodypositive by ELISA and Western blotting. Hewas anergic and had a CD4 count of150 x 109/l and CD4 to CD8 ratio 0 3.Zidovudine 1-2 g/day was started in December1987. He has been asymptomatic and has hadno opportunistic infections. In October 1988he developed lethargy, 10 kg weight loss, andthe loss of proximal limb muscle bulk. Heexperienced "'aching" in his hamstring musclesafter exercise. He was on spironolactone50 mg/day for portal hypertension and oedemasecondary to alcoholic cirrhosis. Examinationshowed ascites and hepatosplenomegaly. His

weight in November 1988 was 59 kg (82A4 kg inJune 1988) and CK 613 u/l (NL 200). Follow-ing withdrawal of the zidovudine muscularsymptoms resolved and the CK fell to 155 u/lin January 1989.

Light MicroscopyBiopsy free vastus lateralis showed slight vari-ation in fibre size with occasional atrophicfibres. There was no myophagia, regeneration,or inflammation. Less than 5% of fibresshowed vesicular change with vesicles 1-2 gmin diameter. The vesicles did not contain fat orglycogen and were identical to those found inthe previous cases. There were 55% type 2fibres and 45% type 1. The mean (SD) type 2fibre size was 33 (8) pm and type 1 33 (8) gm.Electron MicroscopyThere were aggregates of enlarged mitochon-dria measuring 0-1 to 1 2 gm in diameter in thesubsarcolemmal regions. Many of the mito-chondria had lost the normal linear arrange-ment of cristae. Instead, the cristae were arran-ged in a whorled pattern. Some of the cristaehad electron lucent spaces which were single,multiple, or replaced most ofthe mitochondria.Prominent foci ofZ band streaming were foundin a single fibre in which the mitochondrialchange and myofibrillary loss was mostprominent.

DiscussionThe table summarises the clinical and patho-logical data of the six patients. Patients 1 and 2developed a clinical syndrome or proximalmuscle weakness with a normal creatine kinasein the absence of zidovudine treatment. Lightmicroscopy shows vesicular changes in themuscle fibres which ultrastructurally aredilated cistemae ofthe sarcoplasmic reticulum.Patients 3 to 6 had symptoms ranging fromproximal muscle weakness to muscle painsassociated with elevations ofthe creatine kinasein the presence of zidovudine treatment. Lightmicroscopy also showed vesicular changeswhich ultrastructurally are enlarged, electronlucent mitochondria with circular or "whorl"cristae formations. Although vacuolation anddisruption ofa mitochondria are not infrequentartifacts the changes found here seem to us tobe convincing especially the abnormalities ofthe cristae. It is noteworthy that the abnormalmitochondria and vesicles occurred only infibres showing other evidence of injury.Our findings in patients 1 and 2 suggest a

distinct myopathological reaction in AIDS.Dilatations of the sarcoplasmic reticulum (SR)are not considered a result of autolysis (musclespecimens were collected within 30 minutes ofdeath). We have not observed such changes inpostmortem muscle. In addition cell mem-branes were not disrupted and mitochondriawere generally well preserved unlike the chan-ges seen in autolysis. Moreover, control musclefrom cachectic patients without AIDS wasexamined under similar conditions and showedatrophic fibres without the vesicular changesrecorded here. Tomlinson et al in 1969 studied

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Table Clinical and pathological data ofpatients with vesicular changes of skeletal muscle in AIDS

LMfindings (+ to + + + +)Serum Zido-creatine kinase vudine Vesicular

Examination U/L (Normal treat- change %Case Symptoms findings 25-200) ment fibres Necrosis Regen Inflam EMfindings Comment

1 Male, 23 yrs Proximal muscle -muscle wasting 20 - + 10% + + + 1) Dilated(B87/66A and weakness -3/5 proximalB87/66B) limb weakness

2 Male 27 years Proximal muscle -muscle wasting 168(X87/198) weakness -4/5 proximal

limb weakness

Proximal muscleweakness

-muscle wasting 468-4/5 proximalweakness

Deteriorating -muscle wasting 740muscle power -3/5 proximal

Deterioratingmuscle power

Muscle pains

-muscle wasting 1178-2/5 proximallimb weakness-normal 448

- -normal

Muscle pains -4/5 musclepower

Muscle aching -normal

170

930

- + + 20-30% +

sarcoplasmicreticulum2) Disintegrationof sarcomeres

+ - 1) Dilatedsarcoplasmicreticulum2) Distintegrationof sarcomeres

+ - + + + + + + + 1) Cytoplasmicbodies2)Mitochondriaswollen

- + 5% + + ++ + ++ 1)Enlargedelectron lucentmitochondriawith concentric"whorl" cristae2) Cytoplasmicbodies3) Disintegrationof sarcomeres

+ + + 10-20% + + + + + + + As for July '88,but changes moresevere

+ + 5% - - - Enlargedmitochondriawith circularcristae

- - - - - Normalmitochondria

+ + 5%

613 + + 5%

1) Enlargedelectron lucentmitochondriawith concentric"whorl" cristae2) Cytoplasmicbodies3) Sarcomadisruption1) Enlargedmitochondriawith circularcristae2) Z bandstreaming

zidovudineceased Feb.'88

zidovudinerecommencedAugust '88

zidovudineceased

zidovudineceases

2 months afterlast biopsyandwithdrawal ofzidovudinezidovudineceased 3months later;

CK 140 u/L

Muscle power5/5zidovudineceased.

Muscle achingresolved 2months later;CK 155 u/L

the effects of cachexia upon the light micro-scopic appearance of skeletal muscle in 50postmortem cases, none of whom showed thevesicular change described here.'3 Ultrastruc-tural studies of skeletal muscle from patientswith cachexia and malnutrition have shownthinning of myofibrils and widening of theinterfibrillary space, not abnormalities of thesarcoplasmic reticulum.4 15 Patient 1 had diar-rhoea but the electrolytes were normal. Eventhough patient 2 had mild potassium deficiencybefore the development of muscle symptoms,his potassium was normal at the onset andduring muscle weakness. The amphotericinwas stopped in patient 2 several days before theonset of muscle symptoms.

Patients 3 to 6 demonstrated mitochondrialabnormalities in the presence of zidovudinetreatment and not alterations of sarcoplasmicreticulum. Patient 3 also had an inflammatorymyopathy not seen in patients 4 to 6. The firstbiopsy in patient 3 did not show vesicularchange by light microscopy and ultrastructurerevealed mild swelling of mitochrondria onlywhile the patient was first receiving

zidovudine. Zidovudine was stopped and fivemonths later there was persisting inflammationand the development of vesicular change,which included enlarged electron lucent mito-chondria with concentrically arranged cristae.These changes are attributed to the effect ofzidovudine in a coexistent inflammatorymyopathy, as the severity of vesicular changeboth by light and electron microscopy becamepoorer four months after the reintroduction ofzidovudine. In patients 3 and 5 who had themost severe muscle weakness and greatestelevation of the creatine kinase, the mito-chondrial abnormalities were accompanied bydisruption of sarcomeres and cytoplasmicbodies. In patients 4 to 6, who did not have acoexistent inflammatory myopathy, cessationof zidovudine resulted in resolution of themuscle symptoms and return of the creatinekinase to normal after two to three months. Inpatient 4 a repeat biopsy after the withdrawal ofzidovudine showed no vesicular change andnormal ultrastructure.Our studies suggest zidovudine is a

myotoxin and that it exerts its principal

3 Male 34 yrsFebruary 1988(B88/355)July '88 (B88/3662)

December 1988(B88/6481)

4 Male 52 yrs(B88/5933)

(B89/60)

5 Male 50 yrs(B88/5329)

6 Male 46 yrs(B88/6187)

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myopathic effect by disturbing mitochondrialstructure and function. The abnormalities ofmitochondria structure described here aresimilar to those recorded in the drug inducedmyopathies, namely chloroquine and emetine,where there is derangement of cristae andeventual mitochondrial disruption as we havefound.6 17 Our studies confirm previousreports of a necrotising non-inflammatorymyopathy associated with zidovudine treat-ment. 8 9However, we believe vesicular changedue to dilatations of the SR described above, isa distinct entity unrelated to zidovudine. In thepresence of zidovudine, vesicular change inmuscle fibres is due to vacuolation of mito-chondria unrelated to the SR. Vacuolation ofmuscle has been described in AIDS in thepresence and absence of zidovudine treatment.In the report by Stern et al 1987 the vacuolationmeasured 10-50 gm, and was centrally locatedwithin the myofibre.4 The vesicular changes asdescribed by us were not found. Mitochondrialultrastructural abnormalities were not reportedin a patient who received zidovudine anddeveloped vacuolation of muscle described byGorard et al 1988.'9 Vacuolation of voluntarymuscle is recognised in the so called vacuolarmyopathies and includes periodic paralyses,inclusion body myositis, lipid storagemyopathies, glycogenoses, and the oculo-pharyngeal myopathies.20 The diagnoses wereexcluded clinically and pathologically. Thevacuoles in these conditions measure 10-50 umin diameter unlike the 0-1-2 um vesicles foundin our cases.

In conclusion, we have described two dis-tinct myopathological entities in AIDS. Thefirst disorder occurs in the absence ofzidovudine treatment, and is characterised byvesicular change by light microscopy dueultrastructurally to dilations of the sarcoplas-mic reticulum and probably represents aunique cytopathic effect analogous to the"foamy degeneration" associated with otherretroviruses.2'22 The second entity occurs inthe presence of zidovudine treatment and isalso characterised by vesicular change by lightmicroscopy but this change is due to enlarge-ment and electron lucency of mitochondriawhich also show abnormal cristae. Zidovudineis a nucleoside analogue which inhibits the invitro replication of human immunodeficiencyvirus and reduces the intracellular pool ofpyrimidines23 which suggests that it may inter-fere with the homeostasis of mitochondrialDNA in muscle.

We thank Mrs Helen Rodgers for technical assistancewith the electron microscopy and Mrs Dianne Johnstonfor typing. The work was supported by the Neuromus-cular Foundation of Western Australia.

1 Snider WD, Simpson DM, Nielsen S, Gold JWM, MetrokaCE, Posner JB. Neurological complications of acquiredimmune deficiency syndrome: analysis of50 pateints. AnnNeurol 1983;14:403-18.

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