Avaliação da densidade e estrutura óssea de adultos com anemia falciforme

Abstract

Sickle cell anemia is the most frequent hereditary hemoglobinopathy in the world and considered an important public health problem. It is characterized by morphological and functional alterations of red blood cells that cause an extensive set of clinical manifestations associated with vasoocclusion and marked hemolysis that affect several tissues, including bone tissue. The manifestation of these changes is subject to the influence of various factors including the severity of the disease, the clinical history and treatment received throughout life (including transfusions and the consequent iron overload), among others. There are also methodological issues concerning in bone evaluation that need elucidation. The general objective of this thesis was to describe bone health in adult individuals with sickle cell anemia. The results are demonstrated in the form of two original articles. In the first article, we investigated the adequacy of bone mass due to the presence of iron overload, as well as its association with biochemical indicators of hemolysis and iron status. The sample consisted of sixty-eight adults (between 19 and 59 years old) of both sexes, divided into two groups according to the presence (n=18) or absence (n=50) of iron overload indicated by ferritin values >1000 ng/mL. Bone parameters was evaluated by Dual-energy X-ray absorptiometry, (DXA) and included bone mineral density (BMD) data at different sites (lumbar spine, total femur, femoral neck, and forearm) and bone microarchitecture (trabecular bone score, TBS). In the whole group, 56% of the individuals presented low bone mass in at least one of the evaluated bone sites, with greater frequency in the lumbar spine. TBS values are compatible with degraded microarchitecture in more than 50% of individuals. No significant differences were noticed in the bone parameters evaluated between the groups as a function of iron overload. The concentrations of iron, lactate dehydrogenase (LDH), total and direct bilirubin showed an inverse association with various bone parameters evaluated (Spearman correlation, P<0.05). In the second article, we investigated the density, microarchitecture, and bone morphometry of the lumbar spine in eighty-six adult individuals (19 to 59 years old) with sickle cell anemia. Morphometry was evaluated in a subsample of thirty-three people (>40 years old). We regarded yet that more than 60% of individuals with sickle cell anemia had low BMD and moderate or severe fractures in at least one vertebra. In 53.5% of the people, it was possible to identify degradation (total or partial) of bone microarchitecture by TBS. We also observed that the TBS was sensible to demonstrate alteration of bone microarchitecture even in individuals with normal Z-score and without morphological alteration of the spine. The results obtained from the two studies suggest that there is no greater impairment of bone mass among individuals with sickle cell anemia and iron overload. However, the associations between bone parameters with LDH and bilirubin concentrations suggest an influence of hemolysis intensity on the bone health of these individuals. We also suggest that the evaluation of bone microarchitecture may contribute to the early detection of bone changes in these patients and that the morphological study of the spine is elucidative for the analysis of the bone structure of individuals with sickle cell anemia and contributes to the interpretation of bone mineral density changes observed in these individuals.