ESPE Abstracts

Background: Vertebral changes such as biconcave end plate depressions are well described in children with sickle cell disease (SCD). However, as vertebral height reductions are a marker of osteoporosis in children, we aimed to determine whether these could present underlying osteoporosis, by performing transiliac bone biopsies in two patients.

Case 1: A 13-year-old female with SCD, presented with back pain. She had delayed puberty, history of subacute avascular necrosis of shoulder and periostitis of hip. Baseline DXA showed, Whole body less head (WBLH) bone mineral density (BMD) z-score: -1.6, Lumbar spine (LS) BMD z-score: -2. Baseline vertebral fracture assessment (VFA) showed multilevel end plate depressions. DXA after 12 months was stable (WBLH: -0.9, LS:-2.1, no further vertebral changes on VFA). MRI spine confirmed central end plate depressions, with no bone marrow oedema. A bone biopsy was performed due to the persistence of back pain, low BMD and abnormal vertebral imaging. Structural histomorphometric parameters on bone biopsy revealed slightly reduced cortical width (Ct.Wi) and bone volume per tissue volume (BV/TV), normal trabecular indices and osteocyte density. Bone formation rate (BFR/BV) was increased, whereas bone resorption parameters were normal. No mineralisation defect was identified.

Case 2: A 15-year-old female with SCD, with poor adherence to hydroxycarbamide treatment presented with back pain.

Baseline DXA z-scores: WBLH-BMD -0.2 and LS-BMD -0.5; VFA showed multiple endplate depressions with >25% height reductions in the thoracolumbar vertebrae. Repeat DXA at 12 months showed stable BMD, however there was further T12 height reduction on VFA, with improvement in T11. MRI spine showed abnormal STIR signals in L4/L5 and S1. Structural histomorphometric parameters on bone biopsy showed normal Ct.Wi, increased BV/TV, increased BFR/BV and hyperosteocytosis.

Discussion: Both biopsies demonstrated cortical and trabecular indices within the normal range, ruling out osteoporosis. There was, however, increased bone formation, but no evidence of mineralisation defect. Vertebral changes on VFA and abnormal signal on MRI are likely infarcts. This is in line with DEXA BMD reports. Therefore, treatment should focus on optimising SCD treatment and pain management. In equivocal cases diagnosis of osteoporosis should be made on basis of bone histomorphometry via bone biopsy.