Background: This study aims to identify folate-metabolism-related genetic risk factors for low bone mineral density (BMD) during/after pediatric acute lymphoblastic leukemia (ALL) treatment. Patients and methods: We investigated the influence of methylenetetrahydrofolate reductase (MTHFR 677C>T and 1298A>C) and methionine synthase reductase (MTRR 66A>G) single nucleotide polymorphisms (SNPs) on total body BMD (BMDTB) and lumbar spine BMD (BMDLS) in 83 patients. Homocysteine, folate and vitamin B12 were determined. BMD was measured repeatedly using dual-energy X-ray absorptiometry in patients ≥4years (n=68). Results: Carriers of the MTHFR 677 T-allele showed a lower baseline BMDTBthan non-carriers (-0.38 SDS vs. +0.55 SDS, p=0.01) and BMDTBremained lower during/after treatment. MTHFR 677C>T did not influence treatment-related loss of BMDTB(p=0.39). The MTRR 66 G-allele carriers showed a trend towards a lower BMDTBcompared with non-carriers. Combining these two SNPs, patients carrying ≥2 risk alleles had a significantly lower BMDTB(-1.40 SDS) than patients with one (-0.80 SDS) or no risk alleles (-0.31 SDS). Although carriers of the MTHFR 1298A>C had higher homocysteine levels, this SNP was not related to BMDTB. BMDLSof carriers was similar to non-carriers of the investigated SNPs. Conclusions: The MTHFR 677C>T SNP and the MTRR 66A>G SNP were identified as determinants of impaired BMDTBin childhood ALL patients.

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Erasmus MC: University Medical Center Rotterdam

te Winkel, M. L., de Muinck Keizer-Schrama, S., de Jonge, R., van Beek, R., van der Sluis, I., Hop, W., … van den Heuvel-Eibrink, M. (2011). Germline variation in the MTHFR and MTRR genes determines the nadir of bone density in pediatric acute lymphoblastic leukemia: A prospective study. Bone, 48(3), 571–577. doi:10.1016/j.bone.2010.10.163