A lack of this enzyme disrupts the normal balance of fatty acid formation and breakdown. As a result, fatty acids cannot be converted to energy, which can lead to characteristic features of this disorder, such as low blood sugar and cardiomyopathy. By-products of fatty acid processing build up in tissues, which also contributes to the signs and symptoms of malonyl-CoA decarboxylase deficiency. Malonyl-CoA decarboxylase deficiency is inherited in an autosomal recessive pattern. This means that the defective gene is located on an autosome (chromosome 16 is an autosome), and two copies of the defective gene - one inherited from each parent - are required to be born with the disorder. The parents of a child with an autosomal recessive disorder both carry one copy of the defective gene, but are usually not affected by the disorder. Malonyl-CoA decarboxylase deficiency is extremely rare, evidence suggests that it is caused by the abnormality in the protein transcription regulation. Looking at the molecular basis, two distinct homozygous mutations are found to cause Malonyl-CoA  Decarboxylase deficiency in human. The first mutation is the transversion of gene from C to G causing a premature stop signal in the protein. The second mutation is a base pair insertion in the mature RNA that will eventually result in the protein truncation.A research has also confirmed that the homozygous mutation which eventually leads to MCD deficiency is caused by the isodisomy of maternal UPD. This indicates that such disease is likely to be inherited from mother’s gene profile, not from paternal source.
Similar study was conducted in Netherland, and found seventeen reported cases of Malonyl- CoA decarboxylase deficiency in children age range from 8 days to 12 years.Although we have not yet gained a clear understanding of the pathogenic mechanism of this deficiency, some researchers have suggested a brain-specific interaction between Malonyl-CoA and CTP1 enzyme which may leads to unexplained symptoms of the MCD deficiency.Research has found that large amount of MCD are detached in the hypothalamus and cortex of the brain where  high levels of lipogenic enzymes are found, indicating that MCD plays a role in lipid synthesis in the brain. Disturbed interaction between Malonyl-CoA and CPT1 may also contributed to abnormal brain development.Malonyl-CoA decarboxylase plays an important role in the β-oxidation processes in both mitochondria and peroxisome. Some other authors have also hypothesized that it is the MCD deficiency induced inhibition of peroxisomal β-oxidation that contributes to the development delay. Diagnosis
Treatment
See also
Combined malonic and methylmalonic aciduria (CMAMMA)

References
External links
Malonyl-CoA decarboxylase deficiency at NLM Genetics Home Reference