Panniculitis

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Panniculitis is inflammation of the adipose tissue and fits into the larger category of inflammatory skin disorders. It is encountered in dermatopathology specimens.

Classification

  • Lobular - involve fat lobules.
  • Septal - involve interlobular septae.

A simple general DDx

Septal:

Lobular:

DDx by type

Septal:

Lobular:[1]

  • Infectious panniculitis.
  • Erythema induratum.
  • Lupus panniculitis.
  • Pancreatic panniculitis.
  • Alpha1-antitrypsin deficiency.
  • Subcutaneous fat necrosis of the newborn.
  • Sclerema neonatorum.

Specific conditions

Erythema nodosum

General

  • Most common from of panniculitis.[2]
  • Classically on the shins - resolves without scarring.[3]

Causes - mnemonic NODOSUM:[2]

  • 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

Clinical:[4]

  • Painful.
  • Tender.
  • Sudden onset.
  • Heal without scarring.

Gross

  • Red/brown nodules.
    • Classically shins[5] - also knees and ankles.[4]
    • Often bilateral.[4]

Microscopic

Features:[6][7]

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

Notes:

  1. No vasculitis.
  2. +/-Granulomas - within the septa.[8]
  3. No ulceration.[4]

DDx:

Images

Morphea profunda

  • AKA scleroderma panniculitis.

Erythema induratum

General

Features:[6]

Clinical:[7]

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

Microscopic

Features:[6]

  • Predominantly lobular process with:[3]
    • Necrotizing granulomatous inflammation.
    • Necrotizing vasculitis of small/medium sized vessels (early).

DDx:

Images:

Stains

See also

References

  1. 1.0 1.1 1.2 Brinster, NK. (Nov 2008). "Dermatopathology for the surgical pathologist: a pattern-based approach to the diagnosis of inflammatory skin disorders (part II).". Adv Anat Pathol 15 (6): 350-69. doi:10.1097/PAP.0b013e31818b1ac6. PMID 18948765.
  2. 2.0 2.1 Schwartz, RA.; Nervi, SJ. (Mar 2007). "Erythema nodosum: a sign of systemic disease.". Am Fam Physician 75 (5): 695-700. PMID 17375516.
  3. 3.0 3.1 URL: http://www.medscape.com/viewarticle/440356_8. Accessed on: 11 September 2011.
  4. 4.0 4.1 4.2 4.3 Requena, L.; Requena, C. (Jun 2002). "Erythema nodosum.". Dermatol Online J 8 (1): 4. PMID 12165214.
  5. Babamahmoodi, F.; Babamahmoodi, A.; Barani, H.; Delavarian, L. (2012). "Simultaneous occurrence of erythema nodosum in monozygotic twin sisters.". Case Rep Med 2012: 109427. doi:10.1155/2012/109427. PMID 22719770.
  6. 6.0 6.1 6.2 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.
  7. 7.0 7.1 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.
  8. 8.0 8.1 URL: http://missinglink.ucsf.edu/lm/DermatologyGlossary/erythema_nodosum.html. Accessed on: 11 September 2011.

External links