bolt MELAS Syndrome

In hospital, the team assesses the cause of the symptoms, treats seizures and adjusts fluids, nutrition and other support to your blood tests and organ function. Bring your specialist’s emergency instructions so that the team can take your usual health and previous episodes into account. Urgent neurological assessment, seizure management and individual metabolic and organ support are required. The specialist emergency plan should inform care without replacing assessment of the acute presentation. ^{[3, 14]}

Some small studies reported improvement after intravenous arginine. A systematic review found the evidence too weak to establish benefit, and the 2026 consensus still calls its effectiveness unproven. Uncontrolled arginine studies reported clinical signals, but systematic appraisal found no demonstrable efficacy from the available low-quality evidence. The 2026 consensus considers acute IV arginine efficacy unproven. ^{[14, 21, 22]}

Long-term arginine: it is not proven to prevent episodes. If it is part of your plan, ask why it was chosen, how benefit and harms will be checked, and when it should be reviewed. Prophylactic arginine: oral efficacy remains unproven. Any use requires an individual indication, monitoring plan and periodic reassessment. ^{[14, 21, 22]}

See the supplements guide for the evidence on arginine, citrulline and taurine.

Lactate can rise when cells cannot use energy normally. A raised result alone is not the same as dangerous acid buildup in the blood, and it does not show by itself how unwell someone is. Clinicians interpret it alongside symptoms, other blood tests and how the sample was taken. Impaired oxidative metabolism can cause hyperlactataemia. Lactic acidosis additionally involves acid–base disturbance; interpretation requires the clinical context, other biochemical results and pre-analytical factors. ^{[14, 18]}

There are other reasons for a raised lactate result, and a normal result does not rule out MELAS. Your team will decide when measuring it is useful rather than relying on one result to confirm or exclude the diagnosis. Lactate is a supportive investigation with alternative causes of elevation. No isolated threshold confirms or excludes MELAS; testing should be clinically indicated. ^{[14, 15, 18]}

Care: ask for a plan for illness or difficulty eating and drinking. In hospital, fluids, food or glucose support and monitoring are adjusted to your condition. Care: assess the cause of acidosis and individualise hydration, nutrition and glucose management to metabolic status and cardiac/renal function. ^{[3, 14]}

Seizures can happen during or between stroke-like episodes. MELAS can also affect thinking, behaviour and muscle function, and some difficulties may persist after an episode. The pattern varies, so it helps to describe changes in daily life as well as obvious seizures to the neurology team. Seizures can occur during or between stroke-like episodes, alongside variable cognitive, behavioural and muscular involvement. Persistent difficulties and changes in function should inform neurological assessment. ^{[3, 14, 18, 20]}

Seizure treatment depends on the seizure type, other health conditions and the exact genetic diagnosis. Agree what to do if a seizure occurs, including any prescribed rescue treatment and when to get emergency help. The medication safety guide explains why some drug decisions need specialist review. Antiseizure therapy should reflect seizure type, genotype and comorbidities. Establish an individual rescue and escalation plan; see the medication safety guide for genotype-specific considerations. ^{[2, 3, 5, 14]}

Rescue treatment: use only the seizure rescue plan prescribed for you and seek emergency help as directed. Acute seizures: follow the individual rescue plan and emergency pathway; suspected seizure activity during an episode requires prompt treatment. ^{[3, 14]}

Hearing loss and diabetes can occur alongside MELAS, and both deserve attention even when neurological symptoms are the main concern. Their presence and severity vary. This overlap with MIDD is one reason care needs to cover more than the features in the syndrome’s name. Sensorineural hearing loss and mitochondrial diabetes can accompany MELAS, with variable burden and overlap with MIDD. Multisystem care should address these manifestations alongside neurological disease. ^{[7, 23, 24]}

Hearing Management

• Hearing checks: agree a repeat testing schedule with audiology, and report changes between visits. Audiology: obtain baseline and serial assessment; consensus suggests yearly to two-yearly testing, adapted to clinical need. ^{[3, 6]}
• Hearing aids: discuss fitting and adjustments when hearing loss affects communication. Amplification: hearing aid fitting should reflect audiometry, speech understanding and functional communication needs. ^{[3, 6]}
• Cochlear implants: an implant assessment may help if hearing aids no longer provide enough benefit. Small m.3243A>G studies report useful outcomes, but results vary. Cochlear implantation: consider specialist assessment for severe hearing loss with inadequate hearing-aid benefit. Small m.3243A>G series support potential benefit; auditory, cognitive and rehabilitation factors influence outcomes. ^{[3, 6]}

Diabetes Management

• Insulin: needed when your body cannot make enough or glucose levels require it. There is no fixed number of years before everyone needs insulin. Insulin: indicated according to insulin deficiency and glycaemic status; time to insulin dependence varies substantially. ^{[4, 7]}
• Other diabetes medicines: your team may consider options such as DPP-4, GLP-1 or SGLT2 medicines. Evidence specifically in MIDD is limited, and weight, digestion and other risks matter. Other agents: DPP-4 inhibitors, GLP-1 receptor agonists and SGLT2 inhibitors have been proposed, largely using extrapolated evidence. Weight loss, gastrointestinal tolerance and ketoacidosis risk require individual assessment. ^{[4, 7]}

See the MIDD page for a detailed comparison table of MIDD diabetes vs type 1 and type 2.

• The heart muscle or its electrical system can be affected. A person may need checks even before symptoms become obvious. Cardiomyopathy and conduction or rhythm abnormalities can occur in mitochondrial disease; symptoms may not reflect the full degree of involvement. ^[3]
• Care: arrange eye checks with your team. These can assess both mitochondrial retinal changes and diabetes-related eye disease. Care: ophthalmic surveillance should assess mitochondrial maculopathy and other pathology, including diabetic retinopathy; follow-up depends on findings. ^{[3, 8]}
• Digestion: constipation, slow stomach emptying and swallowing difficulties can affect eating. Severe pain, swelling or persistent vomiting needs urgent assessment. Gastrointestinal involvement: dysmotility and dysphagia can compromise nutrition. Acute obstructive symptoms require urgent evaluation. ^[9]
• Kidney problems can affect the filters or the small tubes that control water and minerals. Protein in urine can be one clue. Renal phenotypes include glomerular disease such as FSGS and tubular dysfunction. Proteinuria may be a presenting feature. ^{[3, 10]}
• Growth: children may need monitoring of growth and nutritional intake. Growth: monitor paediatric growth and nutrition in multisystem disease. ^{[14, 18]}

Keep an up-to-date medicine list and an emergency plan agreed with your team. Drug risks depend on the exact diagnosis and your health. Read the medication guide. Review drugs in the context of genotype, organ involvement, indication and duration. Use an individual emergency plan. Medication guide. ^{[1, 2]}

• Valproate: it must not be used in POLG-related mitochondrial disease. In other mitochondrial conditions, specialists may consider it for seizures or mood disorders that have not responded to other treatments, only when there is no liver impairment and other safety requirements are met. Pregnancy and reproductive risks need a separate review. Do not stop prescribed treatment yourself. Valproate: contraindicated in POLG-related disease. The 2024 consensus allows consideration for refractory epilepsy or refractory mood disorders in non-POLG mitochondrial disease without liver impairment, subject to other contraindications and reproductive safety requirements. Specialist supervision is essential; avoid unsupervised withdrawal. ^{[2, 5]}
• Metformin: ask for an individual review; guidance differs and acid buildup risk matters. Metformin: reconcile older avoidance guidance with newer conditional use proposals using individual lactic acidosis risk. ^{[3, 4]}
• Aminoglycosides: review hearing, kidney and genetic risks before use. Aminoglycosides: assess ototoxicity, nephrotoxicity and MT-RNR1 genotype-specific risk. ^{[1, 3]}
• Linezolid: may be needed for some infections; your team may monitor for acid buildup. Linezolid: review indication and duration, with lactate monitoring where appropriate. ^[1]
• Other antibiotics: tell the prescriber your diagnosis and medicine list so risks and alternatives can be checked. Other antibiotics: assess indication, mitochondrial toxicity evidence, organ function and available alternatives. ^{[1, 2]}
• Propofol: a brief anaesthetic dose is different from a long infusion. Ask the anaesthetist to plan for your mitochondrial condition. Propofol: prolonged infusion carries distinct risk from brief induction; perioperative management requires individual assessment. ^{[1, 3]}

Supplements are sometimes included in care, but most have limited evidence that they change the course of m.3243A>G disease. Review what each product is intended to do, possible harms and how its use will be reassessed. The supplements guide explains the research on arginine, citrulline, taurine and other products. Routine supplement combinations lack robust disease-modifying evidence for m.3243A>G. Review the indication, interaction profile, intended outcome and ongoing need for each product. See the supplements guide. ^{[11, 12, 13, 14]}

CoQ10 has limited evidence from small trials in mixed mitochondrial conditions. It has not been shown to stop MELAS progressing. Vitamins or other cofactors may have a specific purpose, but a role in energy production is not itself proof that taking extra helps. Small heterogeneous CoQ10 trials show limited effects and do not establish MELAS disease modification. Other cofactors require individual indications rather than inference of efficacy from biochemical function. ^{[11, 12, 13, 14]}