Sir, This to inform you that I am suffering from pain in my spinal cord I have appointment with Doctor for checkup. Please kindly grant me one day leave on 01/09/2012. I shall be thankful to you. Thanking You S P Sddiqui this need some correction please check it Clive
Here's how I would word it in American English. I don't know if it's formal enough for your country and/or relationship with your superior.
Dear (name),
I am suffering from spinal cord pain for which I need to see a doctor. I have an appointment for a checkup on September 1, 2012. Would you please allow me this one day off? I would appreciate it very much!