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Case based learning: Oxidation of Fatty Acids

A breast fed comatosed[6] infant[1] was brought to ER. his investigation revealed hypoketotic[2] hypoglycemia[3], high concentration of medium chain carboxylic acid, acyl carnitine and acyl glycine[4] in plasma and urine. Hyperammonemia[5] was also present. He was diagnosed as a case of medium chain fatty acyl coA dehydrogenase deficiency.

Lab investigations

Test name                            Units                                        Normal values

blood glucose               2.5 mmol/L                                     6.1 mmol/L

plasma Ammonia      120 micromol/L                    15-18 micromol/L


[1] Significance of Age

Symptoms of MCAD deficiency start appearing at approx from 2nd month to 2nd year but in some case on 2nd day of  birth. Causes of this includes following reasons:

1. During first few days after pregnancy, breast milk  contain mainly colostrum which is rich in protein and required for functioning of digestive tract. As the time progress the fatty content of breast milk become more fatty up to 55% of fats it contains. thats why symptoms starts appearing after approximately 2 month

[2] Hypoketosis

Is mainly due to decrease in  beta oxidation of  medium chain fatty acids (abundant type of fatty acids present in milk) due which less acetyl coA is synthesized and hence the less ketone bodies.

[3] Hypoglycemia

Is mainly due to two causes

1. decrease in availability of  glucogenic substances which is mainly due decrease metabolism of fatty acids.

2. decrease in mitochondrial acetyl co A down regulates the pyruvate carboxylase  enzyme which is involved in the gluconeogenesis.

[4] Acyl carnitine and acyl glycine

Raised levels of these substances shows a type of body compensation by binding of medium chain fatty acid with carnitine and glycine. The products of this reaction are acyl carnitine and acyl glycine and excreted in urine quite easily as compared to free fatty acids

[5] Hyper ammonemia

Two possible causes of hyper ammonemia

1. due to increased metabolism of protein to fulfill the body requirement of glucose

2. due to octanoic acid a medium chain fatty acid and a mitochondrial toxin it causes disruption of ammonia metabolism leads to increased level of ammonia in blood.

[6] Coma

Two possible reason for the coma

1. toxicity of ammonia which leads to impaired citric acid cycle leading to coma and hypoglycemia by decrease in energy production.

2. octanoate  reduce oxidation of glucose and leads to neurological symptoms

Gender discrimination

it is an autosomal recessive disorder therefore no gender discrimination  present in disease

Genetic bases of disease

this disease, the MCAD deficiency has frequency of 1 in almost 17000.

Most probable mutation is A985G type which is 985 gene of cDNA and the locus for this gene is 1p31 i.e short arm of 1st chromosome  at locus no 31. In this type of mutation the adenine is replaced by guanine.


Treatment is prevention, carbohydrate rich diet and avoiding prolonged periods without glucose intake, synthetic enzyme can be injected, in extreme case IV is administered when patient is going into coma.

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