Friday, 10 December 2010

Perforating granuloma annulare

Different clinical variants of granuloma annulare have been described. The most common form, as its name indicates, is an annular lesion. The annular margin is firm to palpation and may be continuous or consist of discrete or coalescent papules in a complete or partial circle. The epidermis is usually normal, but surface markings may be attenuated over individual papules whose colour may be skin coloured, erythematous, or violaceous. The lesions are usually asymptomatic. Reports of an association with diabetes mellitus are controversial. Several other associations have been reported.

There is overlap between the different variants, and more than one morphologic type may co-exist in the same patient. It must be noted that some lesions enlarge as nodules rather than having an annular morphology. A diagnosis of localized annular granuloma annulare is made on clinical examination. Histopathologic examination is necessary when the presentation is atypical. The clinical diagnosis is definitely difficult when annular lesions are absent.

Perforating granuloma annulare was named by Owens and Freeman in 1971. It exhibits transepidermal elimination of degenerating collagen histopathologically, the so called “necrobiotic collagen” hence classified as a secondary perforating disorder. Collagen is a fibre that can undergo degeneration but cannot become necrotic; only cells can undergo necrosis so the term degenerating collagen or collagenolysis is preferred. Perforating granuloma annulare starts clinically as small papules with central umbilications. Lesions may be localized (usually in an acral distribution) or generalized. Perforating granuloma annulare lesions have been present in some of the reported HIV-positive patients with granuloma annulare.

In perforating granuloma annulare there is a superficial area of the so called necrobiosis (better called degenerated collagen, as stated above) and mucin accumulation surrounded by palisading histiocytes, situated beneath a perforation in the epidermis. The so called “necrobiotic material” and mucin are extruded via the perforation. At the margins of the perforation there are varying degrees of epidermal hyperplasia. It should be noted that the epidermal changes are inconspicuous in other variants of granuloma annulare.

Mucinous degeneration of collagen appears bluish or at least shows decrease in the degree of eosinophilic (pink) staining. Mucin can be seen more readily by staining with Alcian blue or colloidal iron.

The differential diagnosis of perforating granuloma annulare includes some dermatoses such as insect bites, molluscum contagiosum, pityriasis lichenoides et varioliformis acuta, transepidermal elimination disorders such as perforating collagenosis and acquired perforating dermatosis, sarcoidosis and papulonecrotic tuberculide. Epithelioid sarcoma may masquerade as perforating granuloma annulare. It should be noted that epithelioid sarcoma that can simulate perforating granuloma annulare, as stated, may also contain mucin. Clues to epithelioid sarcoma include ulceration, cytologic atypia, necrotic foci that include necrotic epithelioid cells and possibly a history of recurrence. Immunohistochemically, epithelioid sarcoma can be distinguished from granuloma annulare by positivity for epithelial membrane antigen and (Cyto)keratin.

The tendency of granuloma annulare to remit spontaneously (but it should be noted that perforating granuloma annulare may leave a hypo- or hyperpigmented scar) complicates accurate assessment of the efficacy of any treatment (such as intralesional triamcinolone 2.5 - 3 mg/mL).

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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