Stridor as the major presenting symptom in riboflavin-responsive multiple acyl-CoA dehydrogenation deficiency.
Inspiratory stridor of unknown origin was the leading clinical symptom in an 11-month-old boy. The stridor increased over a period of 4 weeks, and assisted ventilation became necessary. Selective urinary screening by gas chromatography/mass spectrometry analysis revealed excretion of ethylmalonic and 3-OH-isovaleric acid and of N-isobutyryl-, N-2-methylbutyryl-, N-isovaleryl-, N-hexanoyl- and N-suberylglycine. Neither hypoglycaemia nor metabolic acidosis were noticed. Treatment with 200 mg of riboflavin per day led to a dramatic clinical improvement with restoration of normal respiration and an increase in muscular tone within 2 months. During this period, metabolite excretion in urine completely normalized. Riboflavin-sensitive multiple acyl-CoA dehydrogenation deficiency was confirmed in cultured fibroblasts. With riboflavin supplementation, the development of the child has been favourable, with normal school attendance now at an age of 9 years.


CONCLUSIONS
As respiratory symptoms might precede other symptoms in disorders of mitochondrial oxidation, we propose determination of urinary organic acids in all cases of unexplained laryngeal stridor.
Sperl
W
W
Department of Paediatrics, University of Innsbruck, Austria. w.sperl@lkasbg.gv.at
Geiger
R
R
Lehnert
W
W
Rhead
W
W
D000272:Adipates / Q000652:urine; D002648:Child; D002675:Child, Preschool; D044943:Fatty Acid Desaturases / Q000172:deficiency*; D005347:Fibroblasts / Q000201:enzymology; D005500:Follow-Up Studies; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008314:Malonates / Q000652:urine; D017240:Mitochondrial Myopathies / Q000175:diagnosis* / Q000201:enzymology / Q000235:genetics; D009123:Muscle Hypotonia / Q000175:diagnosis* / Q000201:enzymology / Q000235:genetics; D012135:Respiratory Sounds / Q000209:etiology*; D012256:Riboflavin / Q000627:therapeutic use*
D000272:Adipates; D008314:Malonates; C038080:ethylmalonic acid; C029900:adipic acid; D044943:Fatty Acid Desaturases; D012256:Riboflavin