Late-onset multiple-acyl-CoA-dehydrogenase deficiency-like condition: a case series from the West of Scotland.

Multiple-acyl-CoA-dehydrogenase deficiency (MADD) is a rare metabolic disorder affecting fatty acid and amino acid metabolism. Local experience and evolving literature highlights a paucity of genetically confirmed cases. A retrospective analysis of patients attending the West of Scotland neuromuscular service with a working diagnosis of late-onset MADD was undertaken. Nineteen cases were identified with median onset age of 52 years and female predominance. 8/19 presented with rhabdomyolysis and 11/19 with a subacute myopathy over mean 12.6 months. 14/19 had evidence of a provoking factor prior to clinical presentation and 16/19 had current sertraline use. All cases had abnormal acylcarnitine profiles in keeping with a MADDlike profile and abnormal skeletal muscle biopsies. Abnormal lipid accumulation was seen in 14/19, ranging from mild increase in lipid droplet size to gross lipid excess in seven cases. 4/19 were heterozygous for likely pathogenic ETFDH gene variants; no second variants were identified within the limits of testing available. All showed variable improvement following riboflavin therapy, advice on nutrition and advice on sertraline discontinuation. We suggest a late-onset MADD-like myopathy is much more common in the cohort than primary genetic MADD. Non-genetic and acquired factors may be causative, in keeping with the evolving literature.