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: Dental
A child was brought to OPD with red follicular hyperkeratotic papules over knee.These are areas of normal skin in between.The child also has thickening of palms & soles.The most likely diagnosis is 
Select and explain. 
A. Pityriasis rosea, B. Lichen nitidus, C. Pityriasis rubra pilaris, D. Lichen planus.
C: Pityriasis rubra pilaris
Answer: C: Pityriasis rubra pilaris 
Explanation: Red follicular hyperkeratotic lesions with "islands of sparing" and keratoderma(thickened palms & soles) points out to the diagnosis of Pityriasis rubra pilaris.