851 RIBOFLAVIN-RESPONSIVE (RR) MULTIPLE ACYL-COA DEHYDROGENATION DISORDERS (MAD)

Abstract

RR inborn errors of fatty acid metabolism have been recently identified (Ped. Res. 16, 801 (1982); J. Peds. 103, 394 (1983). Fibroblasts from the first patient described with a clinically RR mild MAD variant oxidized [1-¹⁴C]octanoate (OCT) at 35% of control after culture for 2 weeks in R-free MEM but at 75% of control after culture in 2 mg/L R. This patient's cells oxidized [1-¹⁴C]butyrate (BUT) at 19% of control after culture in R-free MEM and at 72% of control after culture in 2 mg/L R. Assay of acyl-CoA dehydrogenases and electron-transferring flavoprotein in this patient's R-supplemented and -depleted cells and mitochondria have not yet distinguished between FAD-synthesis/transport or FAD-apoenzyme binding defects. Mitochondrial ¹⁴C-FAD content was normal after culture of this patient's cells in 8nM ¹⁴C-R for 24 hours, similar to Dr. E. Christensen's results in cell homogenates (personal communication). Further studies on this RR-MAD patient are in progress. In other experiments, cells from 2 patients with severe MAD variants (Clin. Chim. Acta 66,227 (1976); Helv. Fed. Acta 38,9 (1983)) were also RR in vitro, oxidizing BUT and OCT at 4% and 23% of control, respectively, after culture in R-free MEM and at 16% and 38% of control after culture in 2mg/L R. Since all MAD lines studied here are RR in vitro, careful trials of R supplementation in vivo are justified in suspected MAD patients.

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