Reversal of respiratory failure in both neonatal and late onset isolated remethylation disorders

Respiratory failure is a well-documented potential presentation of inherited isolated remethylation disorders (IRDs). It appears to be a combination of both central and peripheral neuropathy and has previously often been considered to herald an irreversible neurological decline. We present three patients, one with methionine synthase (cblG) and two with methyltetrahydrofolate reductase deficiency (MTHFR). One patient with MTHFR presented in infancy, and other patients in later childhood. All three patients required intubation for respiratory failure but in all three, this was totally reversed by the initiation of medical therapy. This consisted of betaine and folinic acid supplementation in all three, methionine in two and cobalamin supplementation in two. The rate of respiratory improvement was variable, though two of the cases were successful extubated within a week of commencement of medical therapy. We document their subsequent clinical, biochemical and electrophysiological progress and review the potential pathological mechanisms underlying respiratory failure in these disorders.