Riboflavin-responsive multiple acyl coenzyme A dehydrogenase deficiency presenting as a proximal myopathy in a young adult

Adult-Onset Presentation of Glutaric Acidemia Type II With Myopathy

INTRODUCTION

Glutaric acidemia type II (GA II) typically presents with profound metabolic acidosis, hypoketotic hypoglycemia, and mild dysmorphic features in newborns. Since its description, 11 patients with adult-onset GA II have been reported.

CASE REPORT

A 23-year-old woman presented at 6 months gestation with preterm labor and weakness for 3 months. Her weakness worsened to the point of not being able to walk despite treatment with corticosteroids for presumed myositis. Biopsies of skeletal muscle revealed extensive lipid myopathy. Metabolic studies and urine organic acids were suggestive of a multiple acyl-CoA dehydrogenase deficiency. Immunoblot of skin fibroblasts demonstrated a deficiency of electron transfer flavoprotein-ubiquinone oxidoreductase. Treatment with carnitine, riboflavin, and diet restrictions improved muscle strength and decreased urine organic acids.

CONCLUSION

This patient had the unique presentation of GA II with only myopathy. In adults with late-onset weakness, metabolic disorders should be considered in the differential diagnosis.

Riboflavin therapy. Biochemical heterogeneity in two adult lipid storage myopathies

Two unrelated adult males, aged 36 (patient 1) and 25 (patient 2) years, presented with subacute carnitine-deficient lipid storage myopathy that was totally and partly responsive to riboflavin supplementation in the two patients, respectively. Plasma acyl-carnitine and urinary organic acid profiles indicated multiple acyl coenzyme A dehydrogenase deficiency, which was mild in patient 1 and severe in patient 2. The activities of short-chain and medium-chain acyl coenzyme A dehydrogenases in mitochondrial fractions were decreased, especially in patient 2. This was in agreement with Western blotting results. Flavin-dependent complexes I and II were studied by immunoblotting and densitometric quantification of two-dimensional electrophoresis with comparable results. Complex I was present in normal amounts in both patients, whereas complex II was decreased only in the pretherapy muscle of patient 2. Flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN) concentrations in muscle and isolated mitochondria, and the activity of mitochondrial FAD pyrophosphatase, showed that patient 1 had low levels of FAD (46%) and FMN (49%) in mitochondria, with a significant increase (P < 0.01) in mitochondrial FAD pyrophosphatase (273%) compared with controls. Patient 2 had similar low levels of FAD and FMN in both total muscle (FAD and FMN 22% of controls) and mitochondria (FAD 26%; FMN 16%) and normal activity of mitochondrial FAD pyrophosphatase. All of these biochemical parameters were either totally or partly corrected after riboflavin therapy.

Ethylmalonic adipic aciduria--a treatable hepatomuscular disorder in two adult brothers

An adult male presented at 28 years of age with muscle weakness and liver dysfunction. His brother had died suddenly 2 years earlier after presenting with Reye's syndrome. Urine organic acid analysis and muscle and cultured fibroblast fatty acid oxidation studies confirmed a diagnosis of ethylmalonic/adipic aciduria-an inherited defect of fatty acid oxidation. The patient responded favourably to treatment with a low fat/high carbohydrate diet supplemented with riboflavin. This case highlights the importance of considering inborn errors of metabolism, in particular fatty acid oxidation defects, in adults with liver disease, muscle disease or Reye's syndrome.