The goal of this clinical trial is to evaluate the effectiveness of ketogenic diet in patients with MELAS syndrome. The main questions it aims to answer are:

Clarify the curative effects of ketogenic diet in the treatment of MELAS disease.

Prevent the aggravation of MELAS disease, and improve the quality of life of patients.

Provide reliable evidence-based medical basis for the clinical application of ketogenic diet in the treatment of MELAS syndrome patients.

The clinical data of the participants treated with ketogenic diet will be collected, including the completion of ketogenic diet and clinical data at the start of treatment and after 1 month, 3 months, 6 months and 12 months

Ketogenic diet initiation and follow-up:

1. Before starting ketogenic diet treatment, patients with abnormal indexes such as liver, kidney, lipid, humoral immunity, hematuria, routine biochemical, electrolyte, trace elements and bone metabolism should be excluded, energy and nutrients should be calculated according to their height and weight, and patients will be taught with ketogenic diet treatment education
2. Patients were initiated ketogenic diet after a short period of fasting (fasting no more than 48 hours). After treatment was initiated, 13 of the calculated target energy was given on the first day, 23 of the target energy was given on the second day, and the target amount was reached on the third day. Nutritionists made appropriate adjustments to the target energy according to the level of blood keto measured by patients
3. Weekly follow-up via telemedicine system or social media, outpatient follow-up at the initiation of ketogenic therapy and at 1 month, 3 months, 6 months, and 12 months respectively. Outpatient follow-up was done in a joint clinic with a dietitian and a neurologist to evaluate the effects and side effects of ketogenic therapy on a compliant diet and related clinical examinations

Clinical data collection:

1. Demographic information and Medical history collection Gender, age, education level age of onset, genetic test, drug use, past history, personal history, family history
2. Clinical symptom collection According to the Newcastle Mitochondrial Disease Adult Scale(NMDAS), including migraine headaches, seizures, stroke-like episodes and etc.
3. Biochemical indicators Blood glucose, keto, lactate and pyruvate monitoring, dietary status, dietary ratio changes, energy changes, weight changes
4. Cognitive function assessment Cognitive function was assessed using Fepsy software
5. Diagnostic Examination Cranial MRI, scalp EEG

Inclusion Criteria:

• Patients who meet the diagnostic criteria of MELAS and have received MELAS standard therapy but are not satisfied with the therapeutic effect, and voluntarily underwent ketogenic therapy

Exclusion Criteria:

• Diseases with porphyria and disturbances in fatty acid transport and oxidation, severe electrolyte metabolism abnormalities, severe hemodynamic instability, acute respiratory infections, uncontrolled systemic infections, severe liver and renal failure, cholesterolemia (>300mgdl), abnormal coagulation, acute pancreatitis, eating disorders, ketogenic diet intolerance, significant weight loss, poor compliance