A 13-year old child has had recurrent episodes of bone pain.

A 13-year old child has had recurrent episodes of bone pain. He has X rays which show necrosis of the hip. Examination reveals proliferative retinopathy. The following diagnosis is likely ?
a Paget's disease
b Osteopetrosis
c Sickle cell disease
d Thalassemia

c Sickle cell disease -answer