I have been put on Chloroquine to treat my suspected Porphyria Cutanea Tarda.

This is purely an empirical treatment which means treating based on symptoms and not any confirmation of the diagnosis. So, they can confirm the diagnosis using a test of the urine where they test for the presence of Uroporphyrins in the urine but since I am anuric that is ruled out. The blood can be tested for this but no one does it in India apparently.

The other option is a biopsy of the skin where they take a small bit of skin and then analyse it for signs of this disease. However skin biopsies can only be useful if done on a blister that has actually formed and for some reason, my dermatologist says it can be done only on blisters that form on the back of my hand or feet and all the blisters that I get are on the fingers and toes! Also, he says, biopsies are often inconclusive.

Since the symptoms are all in tune with Porphyria Cutanea Tarda, we are going ahead, empirically if you will, and treating it.

Chloroquine, most famously used for treating malaria is supposed to be effective for this disease as well if given over long periods. So, I've been asked to take it for a month and watch out for any rashes or change in vision.

Ha! That's the beauty of medicines these days. They will cure you of one condition but can give you another!