25-hydroxyvitamin D deficiency and bone mineral density alterations in paediatric patients who underwent haematopoietic stem cell transplantation

Objectives: Vitamin D (vD) has a crucial role in maintaining calcium homeostasis and normal bone structure. Several studies reported vD defi ciency as a long-term effect of haematopoietic stem cell transplantation (HSCT) because of reduction in sun exposure, lack of vD in diet, steroid therapy and altered gastrointestinal absorption consequent to intestinal GVHD after HSCT. Little is known about early modifi cations of vD levels following HSCT and its correlation with bone mineral density (MBD). Methods: We performed a retrospective analysis of vD status of 31 paediatric pts (19 male) who underwent 42 HSCT (35 allogeneic, 7 autologous) treated in our Institution for cancer and haematologic diseases between 2006 and 2011. The serum levels of 25-hydroxyvitamin D (25(OH)D) were determined before HSCT and every 3 months for 1 year after HSCT. In addition 6 months after HSCT, BMD modifi cations were analyzed by Dual-Energy x-Ray Absorptiometry (DXA) that allows a non-invasive assessment of bone mineral content. No pts were receiving vD supplements. Median age at HSCT was 9 (range 5-12). vD status was classifi ed on the basis of 25(OH)D serum level according to value reported by National Health and Nutrition Examination Survey as: Defi ciency: <15 ng/ml, Insuffi ciency: 15-29 ng/ml, Adequate: >30 ng/ml. Results: Median pre-HSCT 25(OH)D serum concentration was 24.6 ng/ml (range 12-55.1), with 1 pt/31 (3%) showing defi cient levels, 23/31 (74%) insuffi cient and 7 (23%) adequate levels. Median concentration of 25(OH)D post-HSCT was 13.4 (range 6.3-36.4)[P<0.0001]: 21 pts (68%) has defi - cient serum level, 7 (22%) insuffi cient and 3 (10%) adequate (Table 1). BMD evaluated by DXA 6 months after HSCT showed a trend in line with 25(OH)D serum level: Z-score of global BMD was evocative of osteopenia in 15/31 (48%) pts (range -1.1/-2.1) and of osteoporosis in 1/31 (3%) pt (-2.9). Z-score calculated at lumbar vertebrae revealed osteopenia in 4/31 (13%) pts (range -1.1/-2.3) and osteoporosis in 1 pt (-2.6). Conclusions: This retrospective analysis showed that 25(OH)D serum level decreases markedly and precociously in children treated with HSCT and this is associated with an early reduction of global BMD in nearly 50% of the patients at DXA evaluation. These fi ndings suggest the importance of early monitoring of vD status and BMD in HSCT patients in order to start vD supplementation able to prevent severe vD defi ciency and its complications.