Friday, 7 November 2014

Lichen nitidus pathogenesis

Once considered a tuberculoid reaction, lichen nitidus (Latin nitidus, shiny) is currently regarded as a disorder of unknown aetiology. However, history of exposure to tuberculosis in the “setting of lichen nitidus” should be investigated and when appropriate antituberculosis treatment is initiated.  Actually, lichen nitidus needs to be distinguished from lichen scrofulosorum. While the infiltrate in lichen nitidus ‘hugs’ the epidermis and expands the dermal papilla, the granulomas in lichen scrofulosorum do not cause widening of the papillae. Furthermore, in lichen scrofulosorum, there may be mild spongiosis and exocytosis of neutrophils into the epidermis and the granulomas are typically centred on the hair follicles or sweat ducts.

An “allergen” may cause antigen-presenting cells to activate a cell-mediate response, initiate lymphocyte accumulation, and form the discrete papules.  Actually, Langerhans cells are present in large numbers in the infiltrate. Cytokines may shift the T lymphocyte response towards the T helper (CD4+) 2 subset that has the potential to produce the superficial dermal granulomas seen in lichen nitidus (in comparison, CD8+ lymphocytes play an important role in lichen planus (LP) where there are no granulomas). At each lateral margin of the infiltrate, rete ridges tend to extend downwards and seem to clutch the infiltrate in the manner of a claw clutching a ballDirect immunofluorescence examination of lichen nitidus is usually negative (in comparison, direct immunofluorescence examination of LP shows colloid bodies in the papillary dermis, staining for complement and immunoglobulins, particularly IgM. An irregular band of fibrin is present along the basal layer in most cases. Often there is irregular extension of the fibrin into the underlying papillary dermis).

Lichen nitidus eruption is found on any part of the body but the sites of predilection are the forearms, penis, abdomen, chest and buttocks

Early, tiny LP papules may be clinically and histopathologically indistinguishable from lichen nitidus. Coexistence with LP is common. It might also be associated with atopic dermatitis.

It has been suggested that cases reported in the past as summertime actinic lichenoid eruption (SALE) should be reclassified as actinic lichen nitidus, also called “pinpoint, papular polymorphous light eruption” (PMLE).

Lichen nitidus has followed hepatitis B vaccine and appeared during treatment of hepatitis with interferon-α.

There is not usually an associated systemic condition but associations with some conditions such as Down’s syndrome have been reported. Functional impairment in cellular immunity has been reported in generalised lichen nitidus and lichenoid photo-eruption similar to lichen nitidus has been associated with HIV infection.

Köbner’s phenomenon might occur. Perforating lichen nitidus has been described.

No genetic factors of the disease have been identified; however, familial presentation might be seen. Most cases occur in children or young adults. Its course is unpredictable; it may clear in a few weeks or last a very long time, and may show little or no response to treatment.

Lichen nitidus following hepatitis B vaccine

The lesions are minute shiny flesh coloured papules but can be reddish with various tints. 

This page was last updated in March 2017

Main Works of Reference List (The first eight are my top favourites)

  • British National Formulary
  • British National Formulary for Children
  • Guidelines (BAD - BASHH - BHIVA - Uroweb)
  • Oxford Handbook of Genitourinary Medicine, HIV, and Sexual Health
  • Oxford Handbook of Medical Dermatology
  • Rook's Textbook of Dermatology
  • Simple Skin Surgery
  • Weedon's Skin Pathology
  • A Concise Atlas of Dermatopathology (P Mckee)
  • Andrews' Diseases of the Skin
  • Andrology (Nieschlag E FRCP, Behre M and Nieschlag S)
  • Bailey and Love's Short Practice of Surgery
  • Davidson's Essentials of Medicine
  • Davidson's Principles and Practice of Medicine
  • Fitzpatrick's Colour Atlas and Synopsis of Clinical Dermatology (Klaus Wolff FRCP and Richard Allen Johnson)
  • Fitzpatrick’s Dermatology in General Medicine
  • Ganong's Review of Medical Physiology
  • Gray's Anatomy
  • Hamilton Bailey's Demonstrations of Physical Signs in Clinical Surgery
  • Hutchison's Clinical Methods
  • Lever's Histopathology of the Skin
  • Lever's Histopathology of the Skin (Atlas and Synopsis)
  • Macleod's Clinical Examination
  • Martindale: The Complete Drug Reference
  • Oxford Handbook of Clinical Examination and Practical Skills
  • Oxford Textbook of Medicine
  • Practical Dermatopathology (R Rapini)
  • Sexually Transmitted Diseases (Holmes K et al)
  • Statistics in Clinical Practice (D Coggon FRCP)
  • Stockley's Drug Interactions
  • Treatment of Skin Disease: Comprehensive Therapeutic Strategies
  • Yen & Jaffe's Reproductive Endocrinology