Medium chain acyl-CoA dehydrogenase (MCAD) deficiency is an uncommon medical condition characterized by a deficiency of medium chain acyl-CoA dehydrogenase. This enzyme is responsible for the catabolism of medium chain fatty acids and its deficiency can lead to a variety of potentially life-threatening complications.
Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is a disorder that is inherited via the autosomal recessive inheritance pattern. The inborn inability to catabolize medium chain fatty acids usually causes an abnormal buildup of fat in the hepatic and cerebral regions, alongside a multitude of other sequelae.
The condition is primarily diagnosed during early childhood, although there have been some documented cases where diagnosis was delayed until adulthood  . Patients may be asymptomatic, or experience various symptoms, ranging from vomiting to a comatose state and sudden death  . The symptom mainly related to MCAD deficiency is that of hypoketotic hypoglycemia, which is responsible for an altered mental status, weakness, lethargy or coma in young children or infants. Jitteriness, irritability and epileptic activity may also be manifestations due to which parents seek medical help.
Cardiological abnormalities and related symptomatology have also been documented in cases of infants diagnosed with MCAD deficiency. Pulmonary hemorrhage, ventricular tachycardias and irregular sleep patterns are amongst the symptoms described    . They are typically elicited during a fasting period within the day, or following a confirmed or suspected viral infection. Although no neurological findings are usually present, severe metabolic stress can lead to corresponding deficits  . Furthermore, growth may be slightly hindered and the young patients affected by MCAD deficiency may present with tachypnea, somnolence and hepatomegaly; the latter is very frequently associated with the condition .
Patients who do not manifest symptoms in early life will usually present in adulthood with cephalalgia and vomiting.
The workup involved in the diagnosis of medium chain acyl-CoA dehydrogenase deficiency includes serum and urine laboratory testing and a liver biopsy, if deemed necessary. The first step is the medical history, which, for most of the patients is negative for the condition; this is due to the inheritance pattern of MCAD, the autosomal recessive pattern, which usually leads to no concurrent generations with the same medical condition.
Serum laboratory testing includes electrolytes, blood gasses, glucose and ammonia levels. Typical findings are diminished bicarbonate, an anion gap, slightly or moderately elevated ammonia levels and low blood glucose. In some cases, hypoglycemia-related symptomatology occurs before a measurable hypoglycemia has been established. During pregnancy, prenatal genetic testing renders a diagnosis feasible. Urine testing is carried out in order to eliminate the possibility of ketonuria and to evaluate the acylcarnitine excretion pattern alongside an organic acid profile. Residual enzymatic activity can also be measured, for prognostic and therapeutic reasons .
Finally, a liver biopsy may illustrate wide mitochondrial membranes, large-droplet steatosis and electron-dense mitochondrial matrices, which are indicative of a mitochondrial oxidative disorder but are not pathognomonic of MCAD deficiency.