Cystathionine beta synthase deficiency and brain edema associated with methionine excess under betaine supplementation: Four new cases and a review of the evidence. - Schwahn BC; Scheffner T; Stepman H; Verloo P; Das AM; Fletcher J; Blom HJ; Benoist JF; Barshop BA; Barea JJ; Feigenbaum A (JIMD reports, 2020)