II. Definitions

  1. Mitochondrial Encephalopathy, Lactic acidosis and Stroke-Like Episodes (MELAS Syndrome)
    1. Inherited mitochondrial disorder that manifests with Seizures, strokes, vascular Headaches, Muscle degeneration and growth failure

III. Epidemiology

  1. Onset in children and young adults
    1. Peak onset age 2 to 10 years old
  2. Incidence: 1 in 4000
  3. Gender: Equally affected

IV. Pathophysiology

  1. Maternally inherited (as with all mitochondrial disorders)
    1. Multiple genetic defects cause MELAS, but a single base pair mutation m.3234>G is found in 80% of cases
  2. Progressive mitochondrial disorder primarily affects nerve and Muscle Tissue (highly metabolically active cells)
    1. tRNA mutations alter respiratory chain complex synthesis
    2. Impaired mitochondrial energy production, resulting in anaerobic activity and Lactic Acidosis
    3. Microvascular angiopathy
    4. Impaired cerebral vasodilation

V. Findings

  1. Recurrent Neurologic Episodes
    1. Encephalopathy
      1. Altered Level of Consciousness with episodes
      2. Longterm gradual deterioration of overall cognitive function
    2. Myopathy
      1. Proximal Muscle Weakness
      2. Exercise intolerance
    3. Migraine Headache
    4. Focal neurologic deficits (stroke-like episodes)
      1. Most commonly presents with Hemiparesis, Hemianopia
      2. Do not follow a typical vascular pattern
      3. Cummulative stroke-like events result in progressive neurologic deficits
      4. MRI demonstrates correlating lesions
    5. Seizures
      1. Focal or Generalized Seizures
      2. Younger age of onset may predispose to treatment refractory Seizures
  2. Other Findings in Children
    1. Growth and development is typically normal until symptom onset and diagnosis
    2. Short Stature is common
    3. Less common onset in infants, may be associated with Failure to Thrive, congenital Deafness

VI. Labs

  1. Lactic Acidosis
  2. Muscle Biopsy: Compensatory mitochondrial proliferation
    1. Ragged Red fibers on Gomori Trichome stain
    2. Perivascular Smooth Muscle reacts to succinate dehydrogenase

VII. Diagnosis

  1. Stroke-Like Events before age 40 years old
  2. Encephalopathy with Seizures and Dementia
  3. Serum Lactic Acidosis
  4. Muscle biopsy with ragged red fibers

VIII. Differential Diagnosis

  1. Kearns-Sayre
    1. Associated with Short Stature, Hearing Loss and Ataxia
    2. Distinguished by its Vision related findings (Ophthalmoplegia, Retinal changes) and cardiac defects
  2. Myoclonus Epilepsy with ragged red fibers (MERRF)
  3. Leigh Syndrome

IX. Associated Conditions

  1. Cardiac Conduction Deficits
  2. Diabetes Mellitus

X. Imaging

  1. MRI Brain
    1. Multifocal infarcts that do not follow typical vascular patterns

XI. Management

  1. No specific MELAS treatments are available
  2. Keep Immunizations updated
    1. Childhood Primary Series
    2. Influenza Vaccine
    3. Pneumococcal Vaccine
  3. Seizure Prophylaxis
    1. Avoid Valproate
  4. Vitamin Supplementation
    1. Coenzyme Q10, Creatine and L-Carnitine
      1. May increase mitochondrial energy production and slow disease
    2. L-Arginine
      1. May decrease symptom attacks and severity
      2. Arginine IV 500 mg/kg in children (10 g/m2 in adults) given within 3 hours of attack
      3. Arginine 150 to 300 mg/kg/day orally divided three times daily for prophylaxis of events
  5. Avoid medications that may provoke disease
    1. Valproate (see Seizures above)
    2. Metformin (risk of Lactic Acidosis)
    3. Dichloroacetate (Peripheral Neuropathy risk)
    4. Mitochondrial toxins
      1. Aminoglycosides
      2. Linezolid
      3. Tobacco
      4. Alcohol

XII. Resources

  1. Pia (2022) MELAS Syndrome, StatPearls, Treasure Island, FL
    1. https://www.ncbi.nlm.nih.gov/books/NBK532959/

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Related Studies

Ontology: MELAS Syndrome (C0162671)

Definition (MSH) A mitochondrial disorder characterized by focal or generalized seizures, episodes of transient or persistent neurologic dysfunction resembling strokes, and ragged-red fibers on muscle biopsy. Affected individuals tend to be normal at birth through early childhood, then experience growth failure, episodic vomiting, and recurrent cerebral insults resulting in visual loss and hemiparesis. The cortical lesions tend to occur in the parietal and occipital lobes and are not associated with vascular occlusion. VASCULAR HEADACHE is frequently associated and the disorder tends to be familial. (From Joynt, Clinical Neurology, 1992, Ch56, p117)
Concepts Disease or Syndrome (T047)
MSH D017241
ICD10 E88.41
SnomedCT 39925003, 240097009
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Japanese MELAS症候群, MELASショウコウグン, ミトコンドリア脳筋症・乳酸アシドーシス・脳卒中様発作症候群, ミトコンドリアノウキンショウニュウサンアシドーシスノウソッチュウヨウホッサショウコウグン, MELAS症候群
Swedish MELAS-syndrom
Czech syndrom MELAS, Mitochondrickál encefalomyopatie s mléčnou acidózou a epizodami podobnými mrtvici, MELAS syndrom
Spanish Encefalopatía mitocondrial con acidosis láctica y episodios tipo ictus, Miopatía, Encefalopatía Mitocondrial, Acidosis Láctica y Episodio Similar a ACV, Miopatía, Encefalopatía Mitocondrial, Acidosis Láctica y Episodio Stroke-Like, Miopatía Mitocondrial, Acidosis Láctica y Episodio Tipo Ictus, miopatía juvenil, encefalopatía, acidosis láctica Y ACV, miopatía juvenil, encefalopatía, acidosis láctica Y accidente cerebrovascular (trastorno), miopatía juvenil, encefalopatía, acidosis láctica Y accidente cerebrovascular, Síndrome de MELAS, Miopatía Mitocondrial con Acidosis Láctica y Episodio Similar a Ataque, Síndrome MELAS
French Encéphalomyopathie mitochondriale avec acidose lactique et pseudo accidents vasculaires, Syndrome MELAS, Myopathie mitochondriale-encéphalopathie-acidose lactique
Dutch mitochondriale encefalopathie met melkzuuracidose en stroke-like aanvallen, MELAS syndroom, MELAS-syndroom, Mitochondriale myopathie, melkzuuracidose, 'stroke-like' episoden, Syndroom, MELAS-
Portuguese Encefalopatía mitocondrial con acidosis láctica e episódios tipo ictus, Episódio de Miopatia Mitocondrial, Acidose Láctica, Semelhante a Acidente Vascular Cerebral, Episódio de Miopatia Mitocondrial, Acidose Láctica, Semelhante a Icto Cerebral, Miopatia Mitocondrial, Encefalopatia, Acidose Láctica e Episódios tipo AVC, Síndrome de MELAS, Síndrome MELAS
German mitochondriale Enzephalomyopathie mit Laktatazidose und schlaganfallaehnlichen Episoden, Melas Syndrom, MELAS-Syndrom, Mitochondriale Myopathie, Laktatazidose, schlaganfallähnliche Episode
Italian Encefalomiopatia mitocondriale con acidosi lattica ed episodi simili ad ictus, Miopatia mitocondriale, acidosi lattica ed episodi ictus-simili, Sindrome MELAS
Finnish MELAS-oireyhtymä
Russian MELAS SINDROM, MELAS СИНДРОМ
Polish Zespół MELAS
Hungarian MELAS syndroma, Mitochondrialis encephalomyopathia laktát acidosissal és sztrók-szerű episodokkal
Norwegian Mitokondrial myopati, laktacidose og slagliknede episoder, MELAS-syndrom, MELAS