Objective:

A unique presentation and management of coma linked to hyperammonemia in the setting of undiagnosed organic acid disorder 3-MCC deficiency.

 

Background:

This was a 24-year-old vegetarian Indian male with no past medical history or learning disability who developed rapidly progressive encephalopathy that progressed to coma after strenuous physical activity. Initial evaluation revealed ammonia levels above 300uM and elevated creatine kinase. EEG revealed frequent triphasic waves and neuroimaging was unrevealing. Given lack of improvement with lactulose, patient was initiated on continuous renal replacement therapy, resulting in rapid improvement of mental status.

3-methylcrotonyl-CoA Carboxylase (MCC) deficiency is an autosomal recessive disorder of leucine metabolism, due to mutations on MCCC1 and MCCC2 genes. Our patient was found to have elevated levels of 3-hydroxyisovaleric acid (3-HIVA) in the urine, a characteristic metabolic byproduct found in 3MCC deficiency. Genetic testing revealed an MCCC2 mutation. In the outpatient setting, he was then treated with Carnitine (330mg TID) and instructed to avoid vigorous exercise. With lifestyle modifications and supplementation, our patient returned to his baseline function and continues to live a healthy life.

Design/Methods:

N/A

Results:

N/A

Conclusions:

Given the highly variable nature of 3MCC deficiency, we present a unique presentation of an inborn error of metabolism. Though our patient consumed a diet rich in leucine (lentils/soybeans/dairy products) and regularly performed mild exercise without problems, we hypothesize that his metabolic decompensation was triggered by prolonged time of fasting and strenuous activity. This case highlights the severity of acute metabolic decompensation in patients with inborn errors of metabolism. Furthermore, it demonstrates the value of a thorough investigation for reversible causes of encephalopathy in the Neurological ICU, including broad lab work, imaging, and electroencephalography. Learning of hyperammonemia earlier in the disease course was significant in the treatment and management of a potentially life-threatening yet reversible cause of encephalopathy.