Short-Chain Acyl-CoA Dehydrogenase Deficiency Associated with Early Onset Severe Axonal Neuropathy

Abstract

Two unusual cases of axonal neuropathy associated with short-chain acyl-CoA dehydrogenase (SCAD) deficiency are described. These two unrelated infants presented with profound generalised weakness, particularly affecting the upper limbs. Clinical examination revealed generalised peripheral hypotonia and weakness, with absent deep tendon reflexes. An axonal polyneuropathy was confirmed on electromyogram (EMG) and nerve conduction studies (NCS) and, following an extensive metabolic screen, an acylcarnitine and organic acid profile consistent with a short-chain fatty acid beta-oxidation defect was found. In both cases, SCAD deficiency was confirmed by enzyme analysis. Genetic analysis showed the presence of common gene variations in the SCAD gene. SCAD deficiency is a rare disorder with a wide clinical phenotype. SCAD deficiency associated with axonal neuropathy has not previously been reported. As highlighted in these cases, it may be necessary to include axonal neuropathy as a presenting feature of SCAD.