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How accurate is the diagnosis of Lupus from the results of a skin biopsy? - skin rashes diagnosis

I developed a rash, three weeks ago. It all started with a small hole in the crust of the thigh. Then spread to the stomach, and finally my arms and neck. They begin as small red bumps hard, a kind of pimples, but you can not pop, then turn into crusts slightly indent the skin for several weeks. I have lately felt emotionally Extermely and cried with great ease and usually depressed. I have also omitted some time (and certainly in the not pregnant) The doctor took a skin biopsy in one of the potholes. He said he was looking for eczema, but I do not know if this has anything to do with the type of skin biopsy or test to be ordered. The results came as lupus, but I'm not the butterfly rash or joint pain are symptoms of lupus. My symptoms are rash, no relation to the sun, since the outbreak began in the areas of my body, never the sun. Also had no family history of lupus. How accurate are the results of a skin biopsy? Could it be Lyme disease?