Patients all have biallelic pathogenic mutations in the gene. This means they obtained a mutated SUCLA2 gene from each of their parents. Therefore the protein encoded by the SUCLA2 gene does not work or works suboptimal. Various pathogenic mutations have been described. Most are so-called missense mutations but also splice site mutations occur as well as deletions. Diagnostic testing done by metabolic doctors should include testing in blood plasma and/or dry blood spots. Relevant tests are: lactate, methylmalonic acid and carnitine profiling (increased C4-dicarboxylic carnitine). Increased values are generally found. These parameters can also be abnormal in urine.