Background Medium Chain Acyl Coenzyme A Dehydrogenase Deficiency (MCADD) is the commonest disorder of fatty acid oxidation with a prevalence of up to 10,000 in the UK. The prevalence estimated by the gene frequency is significantly higher, fuelling the argument for universal screening. Neonatal screening has recently begun in some areas of the UK. Most patients present with a high morbidity and mortality (up to 25%), with up to 19% of diagnoses made on postmortem.
Case Description A 16 year old girl presented to her local hospital with an encephalopathy following a 24 hour history of nausea and vomiting and an alcoholic binge 48 hours previously. She was transferred to our PICU as she deteriorated further, while sedated with Propofol. Morphine/ midazolam was substited, but there was marked deterioration over the following 24 hours with left ventricular hypertrophy and global ventricular impairment on echo. Fatty liver was noted on ultrasound. Fluid overload, oliguria and renal failure developed with acidosis, rhabdomyolysis and myoglobinuria. (Creatine Kinase 3577). Continuous veno-venous haemofiltration was commenced with good effect. After 36 hours the possibility of a fatty acid oxidation defect was considered and urine was sent for organic and amino acids and blood acylcarnitine profile. DNA analysis confirmed the diagnosis of late onset MCADD with the patient homozygous for the A985G mutation.
Discussion There are marked similarities in the presentation of MCADD and the Propofol Infusion Syndrome: worsening metabolic and lactic acidosis, cardiovascular collapse with increasing inotropic support, bradyarrhythmias with rhabdomyolysis. Propofol has been shown to impair mitochondrial electron transport in the heart in animal models and there is evidence of multiple disturbances in fatty acid metabolism.
Implications for Practice This case demonstrated the need for a high index of suspicion for MCAD deficiency even if age and presenting features are atypical. We would recommend that excessive alcohol intake and propofol sedation be avoided in MCAD deficiency.