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Propionic acidemia is a rare organic acidemia caused by a deficiency in the enzyme propionyl coenzyme A carboxylase.
Propionic acidemia has an incidence of around 1 in 150,000 in the general population 1.
Around 80% of children with propionic acidemia will present within 3 months of birth with symptoms becoming evident during an episode of metabolic decompensation. These include 1,2:
Symptoms are due to the metabolic derangement caused by the acidemia with severe ketoacidosis and hyperammonemia being present 2.
Chronic and intermittent forms of the disease have also been described 2.
The disease is due to a deficiency in propionyl coenzyme-A (CoA) carboxylase and is inherited in an autosomal recessive pattern. Propionyl CoA carboxylase converts propionyl CoA to methylmalonyl CoA and is involved in the metabolism of several amino acids (e.g. valine and leucine) and odd-numbered chained fatty acids 2. Deficiency of this enzyme results in an accumulation of propionic acid.
Elevated levels of propionylcarnitine on a newborn screening test is present 5.
Cardiomyopathy may be a feature of chronic propionic acidemia so cardiomegaly may be apparent 1.
The imaging signs in propionic acidemia are non-specific 2.
diffuse edema and signal irregularities in the cerebral white matter
with sparing of the basal ganglia 2
in older children
hyperintense lesions in basal ganglia (mainly in the putamen and caudate)
abnormal signal intensity and edema in the cerebral and cerebellar cortices are less common 2
DWI: in both neonates and older children areas of restricted diffusion in affected regions 2
typical pattern during acute decompensation may include 2,4:
NAA level: decreased
glutamate level: decreased
glutamine level: decreased
lactate level: increased
During the chronic untreated form of the disease, abnormal myelination as well as cortical and white matter atrophy can be expected 2.
Treatment and prognosis
Long-term treatment of propionic acidemia is a low protein diet (especially low in the offending amino acids; e.g. valine) to reduce the formation of propionic acid in the body 1. Liver transplantation may be required in some cases where despite dietary modification recurrent episodes of metabolic decompensation still occur 5.
- 1. Baumgartner M, Hörster F, Dionisi-Vici C et al. Proposed Guidelines for the Diagnosis and Management of Methylmalonic and Propionic Acidemia. Orphanet J Rare Dis. 2014;9(1):130. doi:10.1186/s13023-014-0130-8 - Pubmed
- 2. Reddy N, Calloni S, Vernon H, Boltshauser E, Huisman T, Soares B. Neuroimaging Findings of Organic Acidemias and Aminoacidopathies. Radiographics. 2018;38(3):912-31. doi:10.1148/rg.2018170042 - Pubmed
- 3. Grünert S, Müllerleile S, De Silva L et al. Propionic Acidemia: Clinical Course and Outcome in 55 Pediatric and Adolescent Patients. Orphanet J Rare Dis. 2013;8(1):6. doi:10.1186/1750-1172-8-6 - Pubmed
- 4. Davison J, Davies N, Wilson M et al. MR Spectroscopy-Based Brain Metabolite Profiling in Propionic Acidaemia: Metabolic Changes in the Basal Ganglia During Acute Decompensation and Effect of Liver Transplantation. Orphanet J Rare Dis. 2011;6(1):19. doi:10.1186/1750-1172-6-19 - Pubmed
- 5. Shchelochkov O, Carrillo N, Venditti C. Propionic Acidemia. 1993. - Pubmed