Occurrences of methylmalonic aciduria and Hartnup disorder in the same family

Methylmalonic aciduria and Hartnup disorder are two rare autosomal recessively inherited metabolic disorders. We have described the coexistence of these disorders within the same pedigree in two unrelated families. This assocation was not found in 57 other families surveyed because of a proband known to have either methylmalonic aciduria or Hartnup disorder.