Since both C677T and A1298C mutations can influence MTHFR activity and plasma homocysteine concentrations (15, 35), it is intriguing to beleive that mutated alleles of MTHFR increase the risk for developing MS in a gene dose-related manner.To our knowledge, the combined effect of MTHFR genotypes has not been previously analyzed in MS populations and further studies are necessary to understand the dose-dependent association of MTHFR alleles with MS risk. The gene discussed is MTHFR; the disease is myeloid sarcoma.