This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Unknown
A 56-year old man presented with bony pain.  X-ray skull lateral view shows: 
Select and explain. 
A. Pagets disease, B. Hyper osteosis frontalis, C. Fibrous dysplasia, D. Osteopetrosis
B: Hyper osteosis frontalis
Answer: B: Hyper osteosis frontalis 
Explanation: Ref. Grainger and Allison's Diagnostic Radiology. Page. 483
 
Pagets disease of bone affects each person differently . It includes :
1 Bones : Pain in the affected bones is the most common symptom of pagets disease of bone.
  Skull in Pagets disease 

osteoporosis circumscripta: large, well-defined lytic lesion
cotton wool appearance: mixed lytic and sclerotic lesions of the skull
diploic widening: both inner and outer calvarial tables are involved, with the former usually more extensively affected
Tam o'Shanter sign: frontal bone enlargement, with the appearance of the skull falling over the facial bones, like a Tam o' Shanter hat