Short/branched chain acyl-CoA dehydrogenase (SBCAD) deficiency also known as 2-methylbutyryl-CoA dehydrogenase deficiency is a rare disorder of isoleucine metabolism. The clinical spectrum of this disorder has not been clearly defined as few patients with SBCAD deficiency have been described. Very few symptomatic patients have been reported. Several symptomatic patients presented with acute crisis in the newborn period including lethargy, poor feeding, apnea, hypothermia, hypoglycemia, EEG and MRI abnormalities, convulsions, lactic acidosis, respiratory distress, seizures, sepsis, disseminated intravascular coagulation and cerebral hemorrhage. Another group of symptomatic patients presented after the neonatal period with symptoms that include hypotonia, motor delay, strabismus, apnea, infantile spasms, developmental delay, attention deficit hyperactivity disorder, recurrent vomiting and failure to thrive. A mother of one of the affected patients was also diagnosed with SBCAD deficiency but is healthy. Most patients have been diagnosed following positive newborn screening result for C5 elevation or were identified after the diagnosis of SBCAD in a sibling. These individuals have remained healthy, most with little or no treatment.