A 30-years-old patient came with h/o fungicidal poisoning patient is given stomach wash and all treatment is given after 4 days in night patient develop a drop in saturation & pulse is 90/min; the level of consciousness is good. Inv - ABG normal. All blood reports -normal, D-dimer normal. 2D Echo; CXR normal.

The patient is having peripheral as well as central cyanosis ++ saturation on oxygen is around 70%. Our final diagnosis is methemoglobinemia. Sent blood sample for Sr metheglin. What are the differential diagnosis and the treatment for above case?