From OMIM
SCAD deficiency is an autosomal recessive metabolic disorder of fatty acid beta-oxidation. Clinical features are variable: a severe form of the disorder can cause infantile onset of acidosis and neurologic impairment, whereas some patients develop only myopathy. With the advent of screening for inborn errors of metabolism, patients with putative pathogenic mutations but who remain asymptomatic have also been identified (summary by Shirao et al., 2010).  http://www.omim.org/entry/201470

From MedlinePlus Genetics
Short-chain acyl-CoA dehydrogenase (SCAD) deficiency is a condition that prevents the body from converting certain fats into energy, especially during periods without food (fasting).

Signs and symptoms of SCAD deficiency may appear during infancy or early childhood and can include vomiting, low blood glucose (hypoglycemia), a lack of energy (lethargy), poor feeding, and failure to gain weight and grow at the expected rate (failure to thrive). Other features of this disorder may include poor muscle tone (hypotonia), seizures, developmental delay, and a small head size (microcephaly).

The symptoms of SCAD deficiency may be triggered by fasting or illnesses such as viral infections. This disorder is sometimes mistaken for Reye syndrome, a severe condition that may develop in children while they appear to be recovering from viral infections such as chicken pox or flu. Most cases of Reye syndrome are associated with the use of aspirin during these viral infections.

In some people with SCAD deficiency, signs and symptoms do not appear until adulthood. These individuals are more likely to have problems related to muscle weakness and wasting.

The severity of this condition varies widely, even among members of the same family. Some individuals are diagnosed with SCAD deficiency based on laboratory testing but never develop any symptoms of the condition.  https://medlineplus.gov/genetics/condition/short-chain-acyl-coa-dehydrogenase-deficiency