Panniculitis

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Panniculitis is inflammation of the adipose tissue. It is encountered in dermatopathology specimens.

General DDx

Specific conditions

Erythema nodosum

  • Most common from of panniculitis.[1]
  • Classically on the shins - resolves without scarring.[2]

Causes - mnemonic NODOSUM:[1]

  • NO cause (idiopathic) ~ 55% of cases.
  • Drugs (sulfonamides, amoxicillin, oral contraceptives) ~ 5% of cases.
  • Other infections - group A streptococci (streptococcal pharyngitis), Yersinia, chlamydia, mycobacteria, others ~ 30% of cases.
  • Sarcoidosis ~ 7% of cases.
  • Ulcerative colitis & Crohn's disease ~ 2% of cases.
  • Malignancy (leukemia, Hodgkin's lymphoma) ~ 1% of cases

Microscopic

Features:[3][4]

  • Expanded septa between fat lobules - key (low power) feature.
  • Neutrophils.
  • Lymphocytes.
  • Histiocytes.
  • Fibrin.

Notes:

  1. No vasculitis.
  2. +/-Granulomas.[5]

Images:

Erythema induratum

General

Features:[3]

  • Uncommon.
  • Etiology: unknown.

Clinical:[4]

  • Classic location: posterior shins.
  • Ulcerates and scars.

Microscopic

Features:[3]

  • Predominantly lobular process with:[2]
    • Necrotizing granulomatous inflammation.
    • Necrotizing vasculitis of small/medium sized vessels (early).

DDx:

  • Infection.

Images:

See also

References

  1. 1.0 1.1 Schwartz, RA.; Nervi, SJ. (Mar 2007). "Erythema nodosum: a sign of systemic disease.". Am Fam Physician 75 (5): 695-700. PMID 17375516.
  2. 2.0 2.1 URL: http://www.medscape.com/viewarticle/440356_8. Accessed on: 11 September 2011.
  3. 3.0 3.1 3.2 Kumar, Vinay; Abbas, Abul K.; Fausto, Nelson; Aster, Jon (2009). Robbins and Cotran pathologic basis of disease (8th ed.). Elsevier Saunders. pp. 1199. ISBN 978-1416031215.
  4. 4.0 4.1 Mitchell, Richard; Kumar, Vinay; Fausto, Nelson; Abbas, Abul K.; Aster, Jon (2011). Pocket Companion to Robbins & Cotran Pathologic Basis of Disease (8th ed.). Elsevier Saunders. pp. 609. ISBN 978-1416054542.
  5. 5.0 5.1 URL: http://missinglink.ucsf.edu/lm/DermatologyGlossary/erythema_nodosum.html. Accessed on: 11 September 2011.