u. mast cell localization and disease progression R. Gorospe, M. D. Tharp, J. Hinckley, et al, unpublished data). Thus, whereas the local release of bFGF from injured or exercised muscle may normally lead to local muscle healing and regeneration, the chronic release of bFGF by d ystrophin-deficient muscle may result in the excess fibrosis and scarring associated with DMD. This work w1\s supported by NIH grant EY 05985 (to P. A. D.) and grants from the Muscular Dystrophy Association and C.B. Day Foundation (to R. H. B.). The authors are grateful to D r T. L. Munsat for assisrance in obtaining D M D blood samples, to D r Lou Kunkel and Sandra R. Smith for their critical reading of the manuscript, and to Carlene Pavlos for help in preparation and editing of the manuscript References 1. Rowland LP. Biochemistry of muscle membranes in Duchcnne muscular dystrophy. Muscle Nerve 1980;3:3-20 2. Hoffman BP, Gorospe JR. The animal models of Duchenne dystrophy: windows on the pathophysiological consequences of dystrophin deficiency. In: Mooseker MS. Morrow JS, eds. Topics in membranes. New York: Academic, 1991:113-154 '3. Saunders KB, DAmore PA. FGF and TGF-P: actions and intrractions in bicilogical systems. Crir Rev Eukary Gene Express 1991;1:157-172 4 . Abraham JA, Mergia A, Whang JL, et al. Nucleotide sequence of a bovine clone encoding the angiogenic protein, basic fibroblast growth factor. Science 1986;233:545-348 5. hlcNeil PL. Cell wounding and healing: the opening and closing of wounds in the cell membrane pruvides a route for the release of moleculrs that maintain and repair tissue. Am Sci 1991;79: 222-235 6. Morrow NG, Kraus WE. Moore JW, e t al. Increased expression of fibroblast growth facrors in a rabbit skeleral muscle model of exercise conditioning. J Clin Invest 1990;85:1816-1820 7. Schaper W. Development and role of coronary collaterals. Trends Cardiovasc Med 1991;1:256-261 8. Watanabe H, Hori A, Seno M, e t al. A sensitive enzyme immunoassay for human basic fibroblast growth fixtor. Biochem Biophys Res Commun 1991;175:229-235 9. Ii M, Yoshida H , A r m & Y, e t al. Improved enzyme immunoassay for human basic fibroblast growth factor using a new enhanced chemiluminescence system. Biochem Biophys Res Commun 1993;193:540-545 10. Thompson RW, Whalen GF, Saunders KB, et al. Heparinmediated release of fibroblast growth factor-like activity into rhe circulation of rabbits. Growth Factors 1990;3:22 1-229 11. Morandi L, Mora M, Gussoni E, e t al. Dystrophin analysis in Duchenne and Becker muscular dystrophy carriers: correlation with intercellular calcium and albumin. Ann Neurol 1990;28: 614-679 12. DiMario J, Buffinger N, Yamada S, et al. Fibroblast growth factor in the extracellular matrix of dystrophic (mdx) mouse muscle. Science 1989;224:688-690 13. Hellia~ellTR, Gunhan 0, Edwards RHT. Mast cells in neuromuscular diseases. Neurol Sci 1990;98:267-276 .r Myo-Leukoencephalopathy in Twins: Study of 324 3-Myopathy, Encephalopathy, Lactic Acidosis, and Strokelike Episodes Mitochondrid DNA Mutation F. Degoul, PhD," M. Diry," A. Pou-Serradell, MD;) J. Lloreta,? a n d C. Marsac, MD' Two dizygotic twins with myopathy and leukoencephaIopathy are described. The female twin had an incomplete form of MELAS syndrome (myopathy, encephalopathy, lactic acidosis, and strokelike episodes)with severe myopathy, epileptic seizures without strokelike episodes. The male twin presented clinical features exciusively of myopathy and subclinical leukoencephalopathy. The MELAS mitochondrial DNA point mutation (MELAS-3243)was found by southern blot and polymerase chain reaction in muscle, skin fibroblasts, and blood of the female twin and was not detected in the skin fibroblasts nor in the blood of the mother, nor in any of the tissues tested in the male twin. The absence of mutation in male twin tissues raises questions about the pathogenetic significance of the mutation in this family. Degoul F, D i r y M, Pou-Serradell A , Lloreta J, Marsac C. Myo-leukoencephalopathy in twins: study of 3243-myopathy, encephalopathy, lactic acidosis, a n d strokelike episodes mitochondrial DNA mutation. A n n Neurol 1994;35:365-370 Within the past 3 years, at least three specific point mutations (3243,3271, 3250) have been described in the mitochondrial tRNALeu(UUR' gene associated with MELAS (myopathy, encephalopathy, lactic acidosis, and strokelike episodes) syndrome, a maternally inherited syndrome [l, 21 or with mitochondria1 myopathy 131. However, it has been demonstrated recently that in spite of being a high level of concordance between the clinical diagnosis of MELAS syndrome and the presence of the 3243 mutation, this mutation is also exhibited in patients with incomplete MELAS syndrome 141, in asymptomatic relatives of MELAS paFrom "INSERM U75, Paris, France, and tSemice of Neurology, Hospital del Mar, Universitat Autonoma de Barcelona, Barcelona, Span Received Mar 5 , 1993, and in revised form Jul 20 and Aug 27 AcLepted for publication Aug 31, 1993 Address correspondence to Ur Degoul, INSERM U 75, 156 rue de vaugirard, F-75015 Pans, France Copyright 0 1994 by t h e American Neurological Association 365 tients 151,in patients with progressive external ophthalmoplegia (PEO) [GI, and in others (73. All these facts mean that MELAS 3 2 4 3 mutation is not completely specific for MELAS patients, that some patients can present typical clinical features of MELAS syndrome without specific MELAS point mutation and that others, with clinical features o t h e r than those described in MELAS syndrome, can exhibit this mutation. We present here 2 dizygotic twins, female and male patients, with childhood-onset myopathy and leukoencephalopathy discovered by neuroimaging studies. The leukoencephalopathy appeared with features apparently identical t o those recently described in one family with adult-onset dystrophic myopathy and leukoencephalopathy @}. In this study, w e investigated t h e MELAS 3243 mutation in t h e female twin with recognized mitochondrial rnyopathy and epileptic seizures, in her brother with clinical and histopathological myopathy compatible with limb-girdle dystrophy, and in t h e asymptomatic mother. Patients Reports Clinical Data The pedigree is shown in Figure 1. Five members were examined; 1 female patient (Patient 11-2) had muscle weakness, fatigability, and epileptic seizures, and her male twin (Patient 11-1) had only muscle weakness. The other members of the family did not present any neurological symptoms. Patients 11-1 and 11-2 were followed for 20 years for a predominantly proximal muscular deficit without an increase of muscle enzyme activity. The details of the clinical features and laboratory examinations have been published. First, these cases have been published among a series of spinal muscular amyotrophy @} according to their clinical and neurophysiological data [electromyographic (EMG) records and clinical deficit being myogenic proximally and neurogenic distally}. Twelve years later, they have been published as a clearly demonstrated mitochondrial disease (especially in the female) [lo]. The clinical, histopathological data are summarized in the Table. PATIENT 0-1. A 32-year-old man started to complain of abnormal muscle weakness at the age of 7. At the beginning, he complained about distal paresis in his lower extremities. Some years later, weakness involved the proximal four limbs. Recently, neurological examination showed weakness of limb-girdle muscles with bilateral winging scapulae and distal paresis of lower extremities with lateral foot-drop and bilateral hypertrophic calves. He maintained walking capacity. Cognitive functions were normal. He worked as a printer. His daughter, 2 years old, is normal. Muscle biopsy examination showed only a predominance of type I fibers, 2 % ragged red fibers (RRF), fiber splitting, and some fibers with internal nuclei. L] Q myopathy deceased 0 unaffected women leukoencephalopathy oroband Fig 1 Pedigree of the family. Circles = female; squares = male. Open symbols are nonaflected subjects; &shed symbols are subjects clinically aflected; a slash in the symbol indicates death. ties were due to a proximal and a distal muscular weakness. At the age of 28 years, she became wheelchair dependent. The epileptic symptoms improved with time. The neurological examination showed a very severe and diffuse weakness in all proximal and distal muscles. Blood lactate acid level was elevated at rest and further abnormally increased during exercise. Muscle biopsy (delroid) revealed many RRF. Radiolvgical Studies in Brain Leukoencephalopathy without ventricular enlargement was present in both twins. It was defined as confluent, not welldemarcated areas of high-signal intensity on long repetition time (TR 2,500 msec), long echo time (TE 60 seconds), spin echo magnetic resonance images (MRIs) (0.6 T) corresponding with areas of low attenuation on the computed tomogram (CT) (Fig 2). No progression of white matter abnormalities in both patients was observed on CT and MRI images during the past 4 years. Methods and Results Ultrastructural Study of’ Muscle Muscle tissue (deltoid muscle) from Patient 11-1 was fixed in glutaraldehyde and osmium tetroxide and embedded in polar-bed resin. Sections of two blocks were examined by an electron microscope, Philips 301. Most of the muscle fibers contained one or several large subsarcolemmal aggregates of mitochondria (Fig 3), usually protruding in the muscle surface. Mitochondria showed no structural abnormalities except for an increase in electron density of cristae. No intramitochondrial crystalline inclusions were found. Muscle tissue from Patient 11-2 processed with the same method showed intense proliferation of the size and number of mitochondria located in the subsarcolemmal and intermyofibrillar spaces ElOl. D N A Preparation and Southern Blot Analysis A 32-year-old woman had normal motor milestones and intellectual development until the age of 6 PATIENT 11-2. years. Then she experienced exercise-induced walking difficulties due to a foot-drop. At the age of 11, she had the first generalized myoclonic seizure. Afterward, walking difficul- 366 Annals of Neurology Vol 35 No 3 March 1994 Total D N A was extracted after digestion of muscle, blood, and fibroblast cell pellets by proteinase K followed by phenol, phenolichloroform extractions, and southern blot analysis was realized as described previously Ell). Total D N A ( 1 kg) was loaded after restriction with Apa I enzyme on a 1.2% Cliniral and Histopathological Duta Patients 11- 1 11-2 Sex M F Age (yr) 32 32 - + +++t + ++ Symptoms Early fatigability Muscle weakness Respiratory distress Epiieptic seizures Serum lactate level At rest After exercise Muscle biopsy Variability in fiber size Splitting fibers Central nuclei Ragged red fibers Fiber type predominance Fiber type deficiency Mitochondria1 subsarcolemma1 accumulation Radiological srudies in brain CT, low attenuation on the white matter MRI, high signal intensity on white matter Progressivity of leukoencephalopathy ++ - t t - - ++ + ++ + + - + +++ Type I 2B - ++ +++ +++ i f + ++ ++ - - - CT = computed tomography; MRI = magnetic resnnance imaging agarose gel. After transfer, filter was hybridized with a probe encompassing nt 3007 to 4508. The probe used was a purified polymerase chain reaction (PCR) product obtained after amplification with primers N D l F o r and N D l R e v and was radiolabeled by random priming. Oligonucleotides used are as follows: NDIFor: 5 'CCCGATGGrGCAGCCGC3' (3007-3023) and NDlRev: 5'GATGGTAGAGTAGATGACGG3' (4508-4489). The heteroplasmic point mutation at position 3243 according to Anderson's sequence can he detected by southern blot because of the creation of the new restriction site for enzyme Apa I. In normal mtDNA, the probe recognizes fragment restrictions 3822 and 2965; in mutant DNA, the 2965 fragment was cleaved in two smaller, 1781 and 1184 bp. The ratio of mutant D N A to wild-type was obtained by scanning nonsaturated exposures of fragments 2965 to 1 184, after correction by the size of these two fragments, with an image analyzer (Starwise, version 4.1 1, 1991, Instar, Paris, France). By this technique (Fig 4A), we were able to point out the A-G transition in the blood cells and skin fibroblasts in culture from the girl twin. This mutation was also detected in the muscle biopsy in the laboratory of Pr S. DiMauro. Mutated molecules were not derectable in the muscle (not shown), the blood, or in skin fibroblasts in culture ( n o t shown) from the male twin, or in the fibroblasts (not shown) or blood from the mother. By Southern blot, we could quantify the proportion of mutated D N A in total mtDNA. In female twin. the percentage varied from 4 0 F in muscle to 2557 in blood and 4 0 q in skin fibroblasts. To detect the MELAS mutation more sensitively, we performed PCR amplification of fragment encompassing nt 3243. Polymerase Chain Reaction Andljsis Fig 2. Magnetic resonance imaging of Patients II-1 (A)and 11-2 (BJ showing increused signal intensity of the .!upratentorial white matter. Total D N A (0.1 pg) was amplified in a mixture containing 200 FLM of each d N T P with 1 pl of [a - "PldCTP (3,000 Brief Communication: Degoul et al: Myo-Leukoencephalopathy in Twins 367 F i g 3. Electron micrograph of deltoid mztscle biop.cy of Patient 11-1. There is intense prolifration of muscle mitochondria located in the sztbsarcolemmal and intemyofibrillar spaces i x 7,000 before 39% redaction). Ciimmol), 30 pmol of each primer, 2.5 units of TamTaq polymerase (Promega) by 35 cycles of 1 min denaturation at 9OoC, 1 min of annealing at 55"C, and 1 min of extension at 70°C. The primers used to detect MELAS mutation were as follows: primer A: 5 'AGGACAAGAGAAATAAGGCC3 ' (3130-3149) and primer B: S'AAGAGCGATGGTGAGAGCTA3' (3555- 35 36). The amplified fragment (425 bp) was digested overnight with Apcl I and the digestion products were analyzed on a 6g polyacrylamide gel and detected by autoradiography. In this way, we confirmed the presence of the heteroplasmic mutation in the two tested tissues (fibroblasts and blood) from Patient 11-2 and could not detect any mutated molecule in Patient 11-1 nor in the mother's tissues (Fig 4B). Discussion These dizygotic twins are affected by a similar pathology, myopathy, and leukoencephalopathy, but with different clinical expressions. The female patient (Patient 11-2) suffered from a rapidly progressive and severe myopathy of mitochondrial origin (lactic acidosis, RRF, ultrastructural abnormalities, epileptic seizures, presence of MELAS mutation 3243), while the male patient (Patient 11-1) suffered from slowly progressive and well-tolerated myopathy compatible with muscular dystrophy (but with normal creatine kinase enzymatic activity {97 IU]). In our Patient 11-2, the MELAS 3243 Point mutation was found in muscle, blood, and fibroblast tissues with a low percentage of mutated molecules, particularly in muscle (40% mutated mtDNA). In typical MELAS syndromes, >60% of mutated muscle mtDNA has usually been described { 5 ] . Because of the lack of strokelike episodes, this patient could be considered to have an "incomplete" form of MELAS, or an oligosymptomatic form, a group very difficult to classify. In 368 Annals of Neurology Vol 35 No 3 March 1994 Fig 4. (A)Southmi blot analysis of M E L A S (mJlopathy,encephalopathy, lactic acidosis, and strokelike episodes) mutation. B = blood: F = fibroblasts; iM = muscle; C + = other patient with M E U S mutation; C - = control subject: M W = molecular useight, ( B ) Apa 1 digestion of the polymerase chain reaction (PCR)amplified m t ~PCR ~ product ~ . 1425 bpi was cleaved in two smaller fragments 1312 and 113 bpi in mutated mtDNA. B = blood; F = fibroblasts; M = muscle; C = controlsubject. this group Ciafaloni and co-workers [ S } have found that the proportion of mutated mtDNA in muscle was lower than this usually described in typical MELAS syndrome. In Patient 11-1, the MELAS 3243 point mutation was not detected even by PCR amplification in all tested tissues. This fact could be related to the nonmitochondrial features of his myopathy, i.e., clinically and histologically it was quite similar to limb-girdle dystrophy. But a mitochondrial pathology is suggested because of the clear predominance of type I fibers and the abnormal subsarcolemmal accumulation of mitochondria. The absence of detection of MELAS mutation in this male twin's tissues could be also correlated with the benign symptomatology and the lack of clinical central nervous system symptoms. Similar differences on the distribution of the mutant mtDNA in dizygotic twins with M E W syndrome (one clinically affected, the other asymptomatic) also have been mentioned previously [12]. Leukoencephalopathy, without clinical manifestations, could correspond, in our patients, with either a demyelination or a dysmyelination due to developmental disturbances, although the lack of progression of leukoencephalopathy on successive MRI and CT scans suggest a dysmyelinating condition. Similar familial leukoencephalopathy has been recently associated with autosomal recessive inheritance {8]. In our family, we cannot exclude the possibility that the male patient presented just this autosomal recessive disorder of leukoencephalopathy with muscular dystrophy and that the girl patient had a mitochondrial encephalomyopathy associated with the 3243 mutation. This A-G transition could represent a de novo mutation or a maternally inherited mutation present in only some tissues of the mother. This mutation is generalized in patients with MELAS [13}, but the proportion of mutated molecules in the blood cells is lower than in the muscle. We did not find any mutated molecules in blood and fibroblast culture of the mother. We cannot exclude the presence of a few mutated molecules in her muscle, but to our knowledge only one case without mutation in the blood and with mutation in the muscle has been described IS]. Other studies demonstrate that this mutation was found in all progeny of heteroplasmic females but was not retrieved in the blood along all the maternal lineage [MI.These results show that this mutation could appear berween two generations by replication mistakes and/or by amplification of traces of mutated mitochondrial genomes. A recent work emphasizes the fact that the MELAS 3243 mutation found in PEO and atypical MELAS patients could play a pathological role according to the tissue adaptability rl5). Therefore, the MELAS 3243 mutation may not be disease causing in our dizygotic twins. Another less probable possibility would be another mutation associated with the clinical expression of the disease that leads to a phenotype analogous to the muscular dystrophy with leukoencephalopathy. This mutation would probably be nuclear because no mutation was found in the mitochondrial genome associated with MELAS mutation [ 161. Our findings suggest that a possible relationship may exist between mitochondrial myopathy and other types of myopathies with leukoencephalopathy and point out the necessity to look for other abnormal genes or point mutations in nuclear DNA. The absence of MELAS mutation in one of two twins clinically affected raises questions about the pathogenetic significance of this mutation. 1ES (Institut Electricice Sanre) and AFM (Association Franqaise contre les myopathies) are acknowledged for givlng grants to Dr C. Marsac -and IES, a fellowship to F. Degoul. We thank M. Sonnier for her technical help. We gratefully acknowledge Pr S. DiMauro for helpful collaboration (data from female twirl muscie). References 1. Goto Y , Nonaka I, tiorai S. A mutation in the tRNAh"'"UR' gene associated with the MELAS subgroup in mitochondrial encephalopathies. Nature 1990;348:651-55? 2. Goto Y ,Nonaka 1, Horai S. A new mtDNA mutation associated with mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS). Biochem Biophys Acta 1991;IOv:238-240 3. Goto Y , Tojo M , Tohyama J, e t al. A novel point mutation in the mitochondria tRNAk"".UR'gene in a family with mirochondrial myopathy. Ann Neurol 1992;31:672-675 4. lnui K, Fukushima H, Tsukamoto H, et al. Mitochondrial encephalomyopathies with the mutation of the mitochondrial tRATAk"'UUK' gene. J Pediatr 1992; 120:62-66 5. Ciahloni E, Ricci E, Shanske S, et al. MELAS: clinical features, biochemistry and molecular genetics. Ann Neurol 1992;31: 391-398 6. Ciacci F, Moraes CT, Silvestri G, et al. The "MELAS-3243 mutation" in mtDNA is found in m a n y patients with progressive external ophthalmoplegia (PEO). Neurology 1992:42(suppl 3): 417 (Abstract) 7. Shanske A, Shanske S, Silvestri G, et al. MELAS point mutation with unusual clinical presentation. Neurology 1992;42(suppl 3 ) : 417 (Abstract) 8. Van Engelen BGM, Leytcn QH, Bersen PLJA, er al. Familial adult-onset muscular dystrophy with leukoencephalopathy. Ann Neurol 1992;32:577-580 3. Pou Seradell A, Montserrat L, Ugarte A. Les formes intermediaires de I'amyotrophie spinale infantile. Rev Neurol (Paris) 1978;134:35-44 10 Pou Seradell A, Corominas J, Vilaseca MA, e t al. Myopathie e t leucoencephalopathie mitochondriales chez des jumeaux de sexe different. Rev Neurol (Paris) 1991;14!:497-500 11. Nelson I , Degoul F, Obermaier-Kusser B, et al. Mapping of heteroplasmic mitochondrial DNA deletions in Kearns-Sayre syndrome. Nucl Acid Res 1989;1?:8117-8124 12. Penisson-Besnier 1, Degoul F, Uesnuelle C, et al. Uneven distribution of mitochondrial DNA mutation in MERRF dizygotic twins. J Neurol Sci 1992;110:144-148 13. Ciafaloni E, k c c i E,Servidei S, et al. Widespread tissue distribution of a tRNAL"'"UR' mutation in the micochondrial D N A of a patient with MELAS syndrome. Neurology 1391;41:16631665 Brief Communication: Degoul et al: Myo-Leukoencephalopathy in Twins 369 14. Sato W, Hayasaka K, Komatsu K, et al. Genetic analysis of three pedigrees of mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes (MELAS). Am J Hum Genet 1992;50:6~-657 15. Moraes CT, Ciacci F, Silvestri G, et al. Atypical clinical presentations associated with the MELAS mutation at position 3243 of human mitochondrial DNA. Neuromusc Disord 1993;3:43-50 16. Kobayashi Y, Momoi MK, Tominaga K, et al. Respirationdeficient cells are caused by a single point mutation in the mitogene in mitochondrial myopathy, enchondrial tRNALeuiU'rR1 cephalopathy. lactic acidosis and stroke-like episodes (MELAS). Am J Hum Genet 1931;43:590-599 Mitochondrial Myopathy with Progressive Decrease in Mitochondrial tRNALeU(UUR) Mutant Genomes Yasuhiko Kawakami, MD,* Ryoichi Sakuta, MD,S IQyoshi Hashimoto, MD,* Osamu Fujino, MD," Takehisa Fujita, MD," Masatoshi Hida, MD," Satoshi Hora, MD,S Yu-ichi Goto, MD,t and Ikuya Nonaka. M W A female patient with mitochondria1 myopathy had a mitochondrial DNA mutation at nucleotide pair 3243, commonly seen in patients with mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes (MELAS), but unlike MELAS patients, she had no central nervous system symptoms. Muscle weakness, which was most severe when she was 7 years old, improved gradually with age. Comparison of two muscle biopsies obtained at an interval of 12.5 years (7 and 20 years of age, respectively), revealed that the number of ragged-red fibers was markedly decreased and histochemical cytochronie c oxidase activity increased in parallel with the decrease in population of mutant genomes. Kawakami Y, Sakuta R, Hashimoto K, Fujino 0, Fujita T, Hida M. Horai S, Goto Y , Nonaka I. Mitochondrial myopathy with progressive decrease in mitochondrial tRNAk"'"UR' mutant genomes. Ann Neurol 1993;35:370-373 Since the first description of mitochondrial myopathy by Luft and colleagues [l] in 1962, many mitochon- From the "Department of Pediatrics, Nippon Medical School, Tama Nagayama Hospital, Tama, Tokyo, +Division of Ultrastructural Research, National Institute of Neuroscience,National Center of Neurology and Psychiatry (NCNP), Kodaira, Tokyo, and $Department of Human Genetics, National Institute of Genetics, Mishima, Shizuoka, Japan. Received Apr 15, 1993, and in revised form Aug 2. Accepted for publication Aug 3 1, 1993. Address correspondence to Dr Kawakami, Department of Pediatrics, Nippon Medical School, Tama Nagayama Hospital, Tama, Tokyo 206, Japan. drial disorders have been described in which almost 40% of patients have the following three major clinical forms: chronic progressive external ophthalmoplegia (CPEO) including Kearns-Sayre syndrome (KSS); mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes (MELAS); and myoclonus epilepsy associated with ragged-red fibers (MERRF) [2]. Each disorder has disease-specific mtDNA abnormalities including large-scale deletions in CPEO and KSS, point mutations at nucleotide pairs (nt) 3243 and 327 1 in MELAS and 8344 in MERRF. We present a female patient who had an A-to-G substitution at nt 3243 in mtDNA (3243 mutation), commonly seen in patients with MELAS 131 but with the unusual feature of improvement in her muscle weakness. While the 3243 mutation is thought to induce various clinical expressions from none to typical MELAS phenotype, this is the first report describing a patient who had reversible muscle weakness and pathology associated with a change in the mutant genome population. Clinical Summary A Japanese girl first noticed muscle weakness and fatigue at 6 years 8 months of age. There was no family history of neuromuscular disorders. H e r mother and brother were in good health with no muscle weakness or fatigability. She had normal developmental milestones. She was first seen in our clinic at the age of 7 years 4 months when she had marked difhculty in climbing stairs. O n examination, she was a slender girl, 113 cm in height ( - 1.61 SDj and 16.6 kg in weight ( - 1.75 SD). She was intelligent and had never experienced strokelike episodes. She had marked proximal muscle weakness in the lower extremities and moderate weakness in the upper extremities. She could not climb stairs without help and utilized the Gowers' maneuver to arise from the prone position. She had no facial weakness and no external ophthalmoplegia. Deep-tendon reflexes were hypoactive, but she had no pathological reflexes. Except for diffuse muscle atrophy, she had no other neurological abnormalities. O n laboratory examination, routine hematological and blood chemical studies were normal except for the following: creatine kinase, 281 UIL (normal, 18-95 UIL); lactate dehydrogenase (LDH), 1,250 IUiL (normal, 50-400 IUIL); lactate, 25.7 mgidl (normal, 3.3-14.9 mgidl); and pyruvate, 1.42 mgidl (normal, 0.30-0.94 mgidl). Cerebrospinal fluid lactate was 25.3 mgidl and pyruvate 0.76 mgidl. Electromyography (EMG) showed a myopathic pattern. The sensory and motor nerve conduction velocities were normal. She had no learning difficulty and graduated from high school with average grades. Her muscle weakness gradually improved. In high school she climbed stairs with minimal difficulty and could run as well as her friends. Serum lactate levels fluctuated reaching a maximum level of 67.3 mgidl at 10 years of age. At 17 years of age, she began to lose body weight progressively despite adequate food intake. She lost 6 kg over 3 years and this was accompanied by excessive perspiration. At age 20 years, she was 156 cm in height and 28.5 kg in weight. She worked in a department store as a clerk without excessive fatig:ibility. She commuted to the store by city bus with only mild difficulty in climbing up the steps. 370 Copyright 0 1994 by the American Neurological Association