Genetics of Methylmalonic Acidemia Clinical Presentation

Updated: Mar 15, 2019
  • Author: Brendan Lee, MD, PhD; Chief Editor: Maria Descartes, MD  more...
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A history of poor feeding, vomiting, progressive lethargy, floppiness, and muscular hypotonia in a newborn who has been healthy for the first 1-2 weeks of life is typical for methylmalonic acidemia (MMA) mut0 or MMA mut-. These newborns typically have been fed for 1-2 weeks or less.

Older infants or children with one of the other forms of MMA or mild mut- may present for the first time during an episode of decompensation with lethargy, seizures, and hypoglycemia.

Older children or adolescents with the cblC form of MMA may present with progressive myopathy, lower leg hyposensitivity, and thrombosis due to the persistent homocystinuria in the cblC form of MMA. The myopathy may not be reversible despite treatment, leading to continued gait disturbances.

Eye findings (eg, retinopathy, nystagmus, reduced visual acuity), hydrocephalus, and microcephaly have been observed in children with the cblC form of MMA.

Renal disease with reduced glomerular filtration rate (GFR) may be observed at presentation or as a long-term complication.

Family history may be positive for siblings with MMA or siblings who died during the neonatal period for reasons that are not clear.



Symptoms include the following:

  • Lethargy, muscular hypotonia, floppiness

  • Developmental delay

  • Facial dysmorphism (eg, high forehead, broad nasal bridge, epicanthal folds, long smooth philtrum, triangular mouth)

  • Skin lesions (eg, moniliasis)

  • Occasional hepatomegaly

  • Acute onset of choreoathetosis, dystonia, dysphagia, and dysarthria (potentially signs of a stroke)

  • Reduced GFR