• Itching

• Medication history: thiazides, furosemide, beta-blockers, ACE inhibitors, phenothiazines, gold, organic mercurials, chloroquine, mepacrine, methyldopa, quinine, chlorpropamide, tolbutamide, proton pump inhibitors

• Occupational history: (whether the patient is in contact with colour film developer

• Hepatitis C infection: erosive-lichen planus is more common.

• Papular, purplish, flat-topped eruption with fine white streaks lace-like pattern (Wickham’s striae) (Fig. 159.1) over the anterior wrists and forearms, sacral region, ankles, legs and penis.

• Involvement of the skin is characterized by the ‘4Ps’: purple, polygonal, pruritic papules.

• Look into the mouth (buccal mucosa, tongue, gum or lips) for a lace-like pattern of white lines and papules (Fig. 159.2). (Remember that oral lichen planus must be differentiated from leukoplakia.)

• Examine the scalp for cicatricial alopecia.

• Examine the nails for longitudinal ridging, pterygium formation from the cuticle (Fig. 159.3), 20-nail dystrophy dystrophy (roughened nail surface and brittle free nail edge) and total nail loss.

• Comment on eruptions that present along linear scratch marks (Koebner’s phenomenon).

• Comment on the residual hyperpigmented macules that lichen planus leaves in their wake.