Bone diseases of radiological importance
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Blood dyscrasias Sickle cell anaemia This hereditary, chronic, haemolytic blood dis order affects principally black populations. It is characterized by abnormal haemoglobin which results in fragile erythrocytes which become sick-le-shaped under conditions of hypoxia. These abnormal red blood cells have a decreased capacity to carry oxygen and are destroyed rapidly producing anaemia. In homozygotes, the radiographic changes reflect the haemopoietic system's response to the anaemia including: • Increased production of red blood cells and hyperplasia of the bone marrow at the expense of the cancellous bone • Bone infarcts (see Fig. 30.7).
Main radiographic features These can include: • Evidence in the skull vault of: — Thickening of the frontal and parietal bones — Widening of the diploic space — Thinning of the inner and outer tables — Generalized osteoporosis — The hair-on-end appearance (rare) • Evidence in the jaws of: — A generalized coarse trabecular pattern, fewer trabeculae are evident and the spaces between them appear larger — The remaining trabeculae between the roots of the teeth can become aligned horizontally to produce a step ladder appearance — Enlargement of the maxillae, with protrusion and separation of the upper anterior teeth — Osteosclerotic areas resulting from the infarcts — Usually normal teeth with normal lamina dura.
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Fig. 30.7 Sickle cell anaemia. A True lateral skull showing widening of the diploic space and thinning of the inner and outer tables and early hair-on-end appearance anteriorly (arrowed). B Periapical showing the generalized coarse trabecular pattern in the mandible.