Lichen planus pigmentosus is a pigmentary disorder of unknown etiology, with diffuse hyperpigmentation of sun-exposed areas, more commonly seen in some ethnic and racial groups. We report an unusual case of lichen planus pigmentosus in a 40-year-old man with Fizpatrick type III skin that was present in a blaschkoid distribution on the trunk, a distribution that has been rarely reported. This unique presentation of lichen planus pigmentosus may contribute to better understanding of the etiology, as the blaschkoid distribution may reflect underlying cutaneous mosaicism that renders those cells more susceptible to an insult that results in lichen planus pigmentosus. This disorder should be considered in the differential diagnosis of macular hyperpigmentation, especially in those from more commonly affected ethnic and racial groups, even when the distribution is atypical and in the absence of history of sun exposure.

Lichen planus pigmentosus-inversus is rare with only twenty patients (including our patient) formally described in the literature. The reported twenty patients with lichen planus pigmentosus-inversus include eight men and twelve women with ages ranging from 25–84 years (average age of 55.3). Twelve were Caucasian, five were Asian, one was Hispanic and two were of unknown ethnicity. Seventeen out of twenty patients had lesions in the axillae and mild pruritus was present in eight patients. Our patient is the first patient reported to have post-auricular sulcus involvement.

Lichen planus pigmentosus is an uncommon variant of lichen planus that is characterized by the insidious onset of dark brown macules in sun-exposed areas and flexural folds.

Superimposed linear lichen planus is an exceedingly rare disorder, but it has been found in both lichen planopilaris and lichen planus types. A 39-year-old woman is presented showing a segmental and linear lichen planus associated with non-segmental lesions meeting all criteria for the diagnosis of superimposed linear planus pigmentosus. The segmental lesions were always more pronounced.