Lichen planus pigmentosus

Lichen planus pigmentosus, or LPP, is a condition marked by slate-grey pigmentation, mostly on the face and neck. The pigmentation is classically over sun-exposed areas, spread evenly and symmetrically, and it is common in dark-skinned people. On the face it favours the temples — the sides of the forehead — and the area in front of the ears; on the neck it affects all sides. Arms, legs and trunk can also be involved.

The patches are dark brown to grey or grey-blue, round or oval, with irregular and poorly defined borders that gradually enlarge and join up. LPP is usually symptomless, although it can occasionally cause mild itching, which is a marker of activity and progression; the itch is present in the early, active phase and disappears quickly afterwards. Rarely there is a burning sensation. It is usually seen in the third to fifth decade of life, in both sexes and slightly more often in women, and is commonly seen in India, the Middle East and South America.

LPP may run a long clinical course. Treatment involves avoiding the triggers and using applied and oral medicines to settle the inflammatory reaction and reduce the pigmentation. How far the pigmentation fades varies from person to person.

Topical agents include hydroquinone, commonly used in combination with retinoic acid, azelaic acid, kojic acid, glycolic acid and tacrolimus. Medicines taken by mouth include corticosteroids and vitamin A, and other options are tranexamic acid and low-dose isotretinoin. Because the lesions seldom clear completely, lasers or chemical peels may be used alongside the topical agents in selected cases.