Three forms of one disease - Paget disease of the bone.

a. Classical appearances in an unusual location in the scapula

Original case:  http://radiopaedia.org/cases/paget-disease-of-the-scapula

b. Cotton wool appearances of the skull

Original case:  http://radiopaedia.org/cases/paget-disease-cotton-wool-skull

c. Blade of grass appearance of acute Paget disease

Original case:  http://radiopaedia.org/cases/paget-disease-with-blade-of-grass-sign

Cases from Frank Gaillard, Ian Bickle and Andrew Dixon.