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: Orthopaedics
Increased density in skull vault is seen in -a) Hyperparathyroidismb)  Multiple myelomac) Fluorosisd) Renal osteodystrophy 
Select and explain. 
A. acd, B. ad, C. bc, D. bde
A: acd
Answer: A: acd 
Explanation: All the causes of generalized increased in bone density can cause increased density of skull vault — Practical imaging 2nd /e 73
Fluorosis and secondary hyperparathyroidism (renal osteodystrophy) cause increased density of skull vault.