Measurement of methylmalonic acid in the urine is used for the laboratory testing of children with signs and symptoms of methylmalonic acidemia as well as for the evaluation of patients with signs and symptoms related to cobalamin deficiency (vitamin B12).
Elevated levels of methylmalonic acid (MMA) in the blood and urine serum occur when there is a disturbance of the enzymes active in the metabolic pathway. Increased methylmalonic acid in the blood is a rare inherited, autosomal recessive disorder that causes methylmalonic acid metabolism to fail. One specific genetic mutation, 271dupA, represents 40% of the pathological alleles of the disease. The disease includes symptoms such as nausea, vomiting, progressive encephalopathy, convulsions and developmental delays. If the disease is not detected early, the condition worsens as the infant consumes more protein. This leads to oxemia, hyperammonemia, coma and death. If the disease is diagnosed at an early stage, oxemia can be minimized by a low protein diet. As this condition is extremely rare, many infants can die from the disease without being diagnosed.
Methylmalonic acid is also a sensitive indicator of vitamin B12 deficiency, as is the case with pernicious anemia. Measuring methylmalonic acid along with the determination of vitamin B12 is the first step in controlling pernicious anemia. Although both measurements are elevated, the follow-up includes screening for endogenous antibodies, wall cell antibodies (APCA), and determining gastrin levels.
Acquired nutritional deficiencies are much more common than genetic abnormalities and may be due to intestinal malabsorption, reduced digestion or poor nutrition. Elderly patients with cobalamin deficiency may develop peripheral neuropathy, ataxia, loss of balance and vibration sensation, memory impairment, depression and dementia, even without anemia. Other conditions such as kidney failure, hypokalaemia and bacterial overgrowth of the small intestine also contribute to the possible causes of mild methylmalonic oxemia and oxyuria.
Several studies have shown that the determination of methylmalonic acid in serum or urine may be a more reliable indicator of cobalamin deficiency than the immediate determination of cobalamin.
Possible Interpretations of Pathological Values
- Increase: Hereditary disorder (methylmalonic oxemia), pernicious anemia, low B12 levels
Laboratory test results are the most important parameter for the diagnosis and monitoring of all pathological conditions. 70%-80% of diagnostic decisions are based on laboratory tests. Correct interpretation of laboratory results allows a doctor to distinguish "healthy" from "diseased".
Laboratory test results should not be interpreted from the numerical result of a single analysis. Test results should be interpreted in relation to each individual case and family history, clinical findings and the results of other laboratory tests and information. Your personal physician should explain the importance of your test results.
At Diagnostiki Athinon we answer any questions you may have about the test you perform in our laboratory and we contact your doctor to get the best possible medical care.