October 2016 | Case of the Month

1) The diagnosis is lichen planus

2) Koebnerisation can be seen in psoriasis, lichen planus, plane warts, molluscum contagiosum, vitiligo and cutaneous mucinosis
 

• Lichen planus (LP) is a fairly common, itchy, non-infectious rash that usually occurs in adults. The medical term ‘lichen’ refers to small bumps on the skin and the term 'planus’ means flat, together they refer to the characteristic flat topped papules of lichen planus (LP)
• LP is thought to be an immunologically mediated disorder
• Itch is usually very marked
• Distribution
  • Can affect any part of the body
  • Most commonly found on the flexural aspects of the wrists, the ankles and the lumbar region
  • Can become widespread
• Morphology
  • Shiny, flat-topped violaceous papules
  • White lines (Whickham's striae) transverse the surface
  • Linear grouped lesions can grow in scratch marks or other sites of skin trauma (Koebner phenomenon)
  • Papules tend to flatten after a few months and are replaced by hyperpigmentation, which can be intense
• Mucosal lesions
  • LP can affect the mouth and vulva
  • The mouth is involved in approximately 50% of all LP cases, and LP confined to the mouth accounts for about 15% of all cases
  • Lesions on the female genitalia are fairly common and when present are usually part of a more widespread eruption, but occasionally occur in isolation or in combination with oral symptoms
  • Characteristic findings are a white lacework pattern. In the mouth the buccal mucosa is the most commonly affected site. The tongue can also be involved, and less so the gums and lips
• Other affected sites
  • ​Scalp - although itch, erythema, scaling and a scarring alopecia have all been reported, some patients have no scalp changes whilst other have a variant of lichen planus known as follicular lichen planus without any skin or mucocutaneous changes
  • Nails - involved in 10% of cases, fingernails > toenails. Thinning of the nail plate with longitudinal changes predominate. On occasions the nails can be severely affected causing permanent deformity
  • The penis - annular lesions predominate

Please refer to the chapter on lichen planus for more information on the many variants of lichen planus, and management advice.