THE BENEFICIAL EFFECT OF 1,25-DEHYDROXICH OLECALCIFEROL ON THE EXCESSOF BLASTS AND MYELOFIBROSIS IN 2 CASES OF CHRONIC MYELOPROLIFERATIVE SYNDROME

The active metabolite of vitamin D3 1.25 dehydroxicholecalciferol (1.2 5DHCC) is a potent inducer of monocytic differentiation of the myeloid blasts <<in vitro>>. Likewise the inhibiting role of vitamine D3 on b one marrow fibrosis by, among others, a stimulating effect of macropha gic activity is known. However, these actions have seldom been clinica lly demonstrated. Two cases of chronic myeloproliferative syndromes in which treatment with 1.25DHCC was effective are presented. In the fir st case, one patient with polycytemia vera with myelofibrosis and foca l blastosis in the bone marrow achieved disappearance of the excess of blasts and a reduction in the fibrosis (grade III to grade I) upon tr eatment. In the second case, idiophatic myelofibrosis, also with focal blastosis in the bone marrow biopsy, there was no regression of the f ibrosis but the blastosis did disappear. It was concluded that 1.25DHC C may constitute an interesting treatment in this group of diseases th rough the following two mechanisms: limitation of the fibrosis and del ay of blast transformation.