Sunday, December 27, 2009

Methylmalonic acidaemia (MMA)

3 year old female child came with developmental delay, lethargy, seizures and hypoglycemia, MRI brain T2 weighted image at the level of basal ganglia showing bilateral symmetrical hyperintensities in globi pallidi.

MMA encompasses a heterogeneous group of disorders characterized by accumulation of methylmalonic acid and its by-products in biological fluids. These disorders are due to a deficiency of the adenosylcobalamin-dependent enzyme methylmalonyl-CoA mutase (apoenzyme deficiency), a defect in intracellular cobalamin metabolism (coenzyme deficiency), transcobalamin II deficiency, intrinsic factor deficiency, or dietary cobalamin deficiency, which is found in vegetarians. The incidence, as derived form a neonatal screening program, is one in 48,000 live births (6). The actual occurrence, however, is estimated to be one in 25,000 live births.
CT and MR imaging of the brain typically reveal atrophy, delay in myelination, and abnormalities in the basal ganglia, predominantly in the globi pallidi. The globi pallidi are particularly sensitive to mitochondrial dysfunction, and are thus prime targets for injury. MR Spectroscopy may show elevated lactate levels either in CSF or in brain parenchyma i.e regions of infarcts. Differential diagnosis for bilateral globi pallidi lesions are HIE (hypoxic ischemic encephalopathy), kernicterus, mitochondrial encephalopathy etc.

3 comments:

Pramod.K.G said...

In case of basal ganglia lesion with increased lactate in MRS , How will u differentiate with leighs syndrome and hypoxic brain injury ..... how u confirmed MMA ..

Dr.Manju.Y.C said...

Dear Dr.Pramod, HIE will have typical history and clinical findings. Radiologically HIE will have elevated lactate levels and Lactate:creatinine ratio will be more than 1.5. where as Leighs syndrome will have different clinical setting and MRS will show elevated lactate levels but same is also seen in CSF unlike HIE. It is very difficult to differentiate Leighs from MMA radiologically. In our case patient had increased serum levels of methylemalanoic acid and also urine excretion. So diagnosis is most of the times by clinical/biochemical and radiological correlation.

Pramod.K.G said...

Thank you for your feed back , i am very much pleased to your response . your blog is very informative ....

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