Unilateral lichen planus along the lines of Blaschko: a rare clinical presentation.

A 34 year man presented to us with itchy lesions on one half of the trunk for the past two months. The lesions started as erythematous to violaceous papules and plaques on the flank and gradually increased in number to involve the left side of the trunk (Figure 1 and 2). Some areas showed the Koebner phenomenon. These lesions were distributed along the lines of Blaschko. Examination of the oral mucosa and nails was within normal limits. There was no history of drug intake, or topical applications prior to the onset of the lesions. He did not have any other known co-morbidities. A differential diagnosis of lichen striatus, lichenoid herpes zoster, linear epidermal nevus and linear psoriasis was considered. A routine hemogram liver function tests and thyroid function tests were normal. Serological tests for hepatitis B, hepatitis C, HIV and syphilis were negative. A skin biopsy was performed which showed hyperkeratosis, acanthosis,