Mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) is one of the family of mitochondrial diseases, which also include MIDD (maternally inherited diabetes and deafness,  MERRF syndrome, and Lebers hereditary optic neuropathy. It was first characterized under this name in 1984. A feature of these diseases is that they are caused by defects in the mitochondrial genome which is inherited purely from the female parent. The most common MELAS mutation is mitochondrial mutation, mtDNA, referred to as m.3243A>G. Signs and symptoms
MELAS is a condition that affects many of the bodys systems, particularly the brain and nervous system (encephalo-) and muscles (myopathy). In most cases, the signs and symptoms of this disorder appear in childhood following a period of normal development. Children with MELAS often have normal early psychomotor development until the onset of symptoms between 2 and 10 years old. Though less common, infantile onset may occur and may present as failure to thrive, growth retardation and progressive deafness. Onset in older children typically presents as recurrent attacks of a migraine-like headache, anorexia, vomiting, and seizures. Children with MELAS are also frequently found to have short stature.Most people with MELAS have a buildup of lactic acid in their bodies, a condition called lactic acidosis. Increased acidity in the blood can lead to vomiting, abdominal pain, extreme tiredness (fatigue), muscle weakness, loss of bowel control, and difficulty breathing. Less commonly, people with MELAS may experience involuntary muscle spasms (myoclonus), impaired muscle coordination (ataxia), hearing loss, heart and kidney problems, diabetes, epilepsy, and hormonal imbalances.
Fishy smelling urine is a primary identifying symptom in infant children (Trimethylaminuria literally meaning "trimethylamine in urine"). Trimethylamine is also released in the persons sweat, reproductive fluids, and breath, and can give off a fishy odor when the concentration of trimethylamine is high enough to be detected. The intensity of the smell is directly correlated with the concentration of trimethylamine in the bloodstream. Some people with trimethylaminuria report having a strong odor all the time, but when in a clinical setting most have only moderate to no smell, depending on diet and the severity of their FM03 mutation. In a study by Wise PM, of 115 identified tmau subjects, 0% had a smell detectable at a social distance and only 5% had some minor malodour when sniffing their palms. After a choline challenge load test (intentionally ingesting a TMA precursor) only 10% expressed a smell at a social distance, suggesting that those that produced odour had a more severe form of FMO3 impairment. Smell events are often sporadic and episodic in nature (based on diet over the previous 24 hours), making it often difficult to diagnose by smell alone. Individuals with this condition do not have any physical symptoms, and they typically appear healthy.The condition seems to be more common in women than men, for unknown reasons. Scientists suspect that such female sex hormones as progesterone and estrogen aggravate the condition. According to several reports, the condition worsens around puberty.