Which disease causes characteristic 'hair on end appearance' in X-ray due to its pathological process?

In the thalassemias, overactivity of the marrow as a result of ineffective erythropoiesis and hemolysis leads to widening of the medullary cavity and thinning of coical bone. The skull radiograph shows widening of the diploic space, giving the typical "hair-on-end" appearance. Overgrowth of the maxillary and temporal bones reduces the volume of the sinuses. The thickened cranium and prominent cheek bones, depressed nasal bridge, and overgrowth of the maxillae produce a distinctive appearance. Ref: Children's Ohopaedics and Fractures edited by Michael Benson, John Fixsen, Malcolm Macnicol, Klausdieter Parsch, 2010, Page 129.