This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous, Subject name: Radiology
A middle aged woman with history of backache underwent a Schober test and came as positive. She had hyperpigmented nose and ears. Looking at this radiograph, most likely diagnosis is:(AIIMS 2017) 
Select and explain. 
A. Ankylosing spondylitis, B. Degenerative disc disease, C. Ochronosis, D. Fluorosis
C: Ochronosis
Answer: C: Ochronosis 
Explanation: Ans. C OchronosisImage shows Intervertebral disc calcification commonly seen in alkaptonuria due to deposition of homogentisic acid. Schober's test is non-specific test that denotes loss of elasticity of spine. Hyperpigmented cartilage is another clue that points towards Alkaptonuria/Ochronosis.