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Genetic and Rare Diseases Information Center (GARD)

Mitochondrial encephalomyopathy lactic acidosis and stroke-like episodes

Other Names for this Disease
  • MELAS syndrome
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What are the signs and symptoms of Mitochondrial encephalomyopathy lactic acidosis and stroke-like episodes?

The signs and symptoms of MELAS often appear in childhood following a period of normal development. Early symptoms may include muscle weakness and pain, recurrent headaches, loss of appetite, vomiting, and seizures. Most affected individuals experience stroke-like episodes beginning before age 40. These episodes may involve temporary muscle weakness on one side of the body, altered consciousness, vision abnormalities, seizures, and severe headaches resembling migraines. Repeated stroke-like episodes can progressively damage the brain, leading to vision loss, problems with movement, and a loss of intellectual function.[1]

Many people with MELAS have a buildup of lactic acid in their bodies (lactic acidosis). This can lead to vomiting, abdominal pain, extreme fatigue, muscle weakness, and difficulty breathing. Involuntary muscle spasms, impaired muscle coordination, hearing loss, heart and kidney problems, diabetes, and hormonal imbalances may also occur.[1]

Last updated: 12/3/2013

The Human Phenotype Ontology provides the following list of signs and symptoms for Mitochondrial encephalomyopathy lactic acidosis and stroke-like episodes. If the information is available, the table below includes how often the symptom is seen in people with this condition. You can use the MedlinePlus Medical Dictionary to look up the definitions for these medical terms.

Signs and Symptoms Approximate number of patients (when available)
Abnormality of mitochondrial metabolism 90%
Cerebral ischemia 90%
Developmental regression 90%
EMG abnormality 90%
Hemiplegia/hemiparesis 90%
Migraine 90%
Muscle weakness 90%
Myopathy 90%
Abdominal pain 50%
Amaurosis fugax 50%
Anorexia 50%
Aplasia/Hypoplasia of the cerebellum 50%
Attention deficit hyperactivity disorder 50%
Cerebral calcification 50%
Cerebral cortical atrophy 50%
Decreased body weight 50%
Decreased nerve conduction velocity 50%
Hallucinations 50%
Incoordination 50%
Involuntary movements 50%
Memory impairment 50%
Nausea and vomiting 50%
Pancreatitis 50%
Ptosis 50%
Reduced consciousness/confusion 50%
Respiratory insufficiency 50%
Sensorineural hearing impairment 50%
Short stature 50%
Type II diabetes mellitus 50%
Visual field defect 50%
Abnormality of neuronal migration 7.5%
Abnormality of retinal pigmentation 7.5%
Abnormality of temperature regulation 7.5%
Abnormality of the genital system 7.5%
Abnormality of the liver 7.5%
Abnormality of the macula 7.5%
Abnormality of the pinna 7.5%
Abnormality of the renal tubule 7.5%
Abnormality of visual evoked potentials 7.5%
Anterior hypopituitarism 7.5%
Aortic dilatation 7.5%
Aortic dissection 7.5%
Apnea 7.5%
Autism 7.5%
Cataract 7.5%
Congestive heart failure 7.5%
Constipation 7.5%
Delayed skeletal maturation 7.5%
EEG abnormality 7.5%
Feeding difficulties in infancy 7.5%
Gingival overgrowth 7.5%
Glomerulopathy 7.5%
Goiter 7.5%
Hypercalciuria 7.5%
Hypertelorism 7.5%
Hypertension 7.5%
Hyperthyroidism 7.5%
Hypertrichosis 7.5%
Hypertrophic cardiomyopathy 7.5%
Hypoparathyroidism 7.5%
Hypopigmented skin patches 7.5%
Hypothyroidism 7.5%
Ichthyosis 7.5%
Intestinal obstruction 7.5%
Malabsorption 7.5%
Mask-like facies 7.5%
Microcephaly 7.5%
Multiple lipomas 7.5%
Muscular hypotonia 7.5%
Myalgia 7.5%
Nephrotic syndrome 7.5%
Neurological speech impairment 7.5%
Nyctalopia 7.5%
Ophthalmoparesis 7.5%
Optic atrophy 7.5%
Paresthesia 7.5%
Premature loss of teeth 7.5%
Primary adrenal insufficiency 7.5%
Proteinuria 7.5%
Pulmonary embolism 7.5%
Pulmonary hypertension 7.5%
Renal insufficiency 7.5%
Skeletal muscle atrophy 7.5%
Spontaneous hematomas 7.5%
Sudden cardiac death 7.5%
Thyroiditis 7.5%
Tremor 7.5%
Type I diabetes mellitus 7.5%
Ventriculomegaly 7.5%
Visual impairment 7.5%
Bilateral sensorineural hearing impairment -
Congenital cataract -
Cortical visual impairment -
Dementia -
Diabetes mellitus -
Encephalopathy -
Episodic vomiting -
Generalized tonic-clonic seizures -
Growth abnormality -
Hemianopia -
Hemiparesis -
Lactic acidosis -
Left ventricular hypertrophy -
Mitochondrial inheritance -
Mitochondrial myopathy -
Ophthalmoplegia -
Progressive sensorineural hearing impairment -
Ragged-red muscle fibers -
Stroke-like episodes -
Wolff-Parkinson-White syndrome -

Last updated: 7/1/2016

The Human Phenotype Ontology (HPO) has collected information on how often a sign or symptom occurs in a condition. Much of this information comes from Orphanet, a European rare disease database. The frequency of a sign or symptom is usually listed as a rough estimate of the percentage of patients who have that feature.

The frequency may also be listed as a fraction. The first number of the fraction is how many people had the symptom, and the second number is the total number of people who were examined in one study. For example, a frequency of 25/25 means that in a study of 25 people all patients were found to have that symptom. Because these frequencies are based on a specific study, the fractions may be different if another group of patients are examined.

Sometimes, no information on frequency is available. In these cases, the sign or symptom may be rare or common.

  1. Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes. Genetics Home Reference. November 2006; Accessed 10/17/2011.

Other Names for this Disease
  • MELAS syndrome
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.