How do you explain this persistent pruritic rash?

Case 1:

For 9 months, a 39-year-old woman has had a pruritic rash on the posterior portion of one thigh. She had consulted another physician, who prescribed a medication that she does not recall, but there was no improvement.

A potassium hydroxide evaluation confirmed the diagnosis of tinea corporis, E. The pruritic annular scaling macules are characteristic.

Impetigo is usually limited to one location for a few weeks before it spreads. Contact dermatitis does not have discrete borders and is rarely unilateral. Granuloma is not as crusty as tinea corporis and is usually asymptomatic. Moreover, because granuloma typically occurs over joints, the hands and feet are common sites. Psoriasis is not usually unilateral and does not typically show central clearing.