Sweet’s Syndrome (aka acute febrile neutrophilic dermatosis)

In the Rapid Review series, I briefly review the key points of a clinical review paper (which often extends to multiple papers because I can’t help myself). The topic this time: Sweet’s syndrome (aka acute febrile neutrophilic dermatosis)

The papers: 

SWEET RD. AN ACUTE FEBRILE NEUTROPHILIC DERMATOSIS. Br J Dermatol. 1964 Aug-Sep;76:349-56. doi: 10.1111/j.1365-2133.1964.tb14541.x. PMID: 14201182 (This is the original publication, by Sweet). 

Korkut M. A dermatologic emergency; Sweet’s syndrome. Am J Emerg Med. 2019 Sep;37(9):1807.e1-1807.e3. doi: 10.1016/j.ajem.2019.06.012. Epub 2019 Jun 5. PMID: 31280940

Cohen PR. Sweet’s syndrome–a comprehensive review of an acute febrile neutrophilic dermatosis. Orphanet J Rare Dis. 2007 Jul 26;2:34. doi: 10.1186/1750-1172-2-34. PMID: 17655751

What is it?

Sweet’s syndrome is a rare inflammatory skin condition characterized by a tender rash and fever caused by neutrophilic infiltration of the skin (hence the name acute febrile neutrophilic dermatosis).

What are the symptoms?

The core symptoms are a high fever and tender erythematous skin lesions (which can be nodules, papules, or plaques). The lesions are often confused with cellulitis, especially given the fever. You will also see constitutional symptoms such as fatigue, myalgias, and weight loss. 

There is a long list of other potential symptoms, as neutrophil infiltration can occur in basically every organ system

What is the etiology?

There are three primary etiologies: idiopathic (or classical), malignancy associated, and drug-induced. Hematologic cancers are the most common malignant cause. It has been associated with a number of drugs, but the most common is granulocyte-colony stimulating factor. 

There is also an association with pregnancy and inflammatory bowel disease.

How is it diagnosed?

Official diagnosis requires a skin biopsy, and so will not be finalized in the emergency department. I think our just is just to recognize it in the setting of a febrile patient with a tender red rash.

The diagnosis requires both:

• Abrupt onset of painful erythematous plaques or nodules
• Histopathologic evidence of a dense neutrophilic infiltrate without evidence of leukocytoclastic vasculitis

Plus 2 of:

• Fever
• An association with an underlying hematologic or visceral malignancy, inflammatory disease, or pregnancy, or preceded by an upper respiratory or gastrointestinal infection or vaccination
• Excellent response to systemic corticosteroids
• Abnormal lab values at least 3 of:
  • ESR >20 mm/hr
  • Elevated CRP
  • WBV > 8,000
  • >70% neutrophils

How is it treated?

Systemic corticosteroids (oral prednisone) are the first line therapy. 

If it is thought to be medication related, obviously stop the medication. It is commonly associated with malignancy, especially hematologic malignancies, and therefore some sources suggest further investigations for an underlying cause. 

What is the prognosis?

The course is usually benign, but it is often recurrent (especially if there is an underlying cause). 

My primary take home

This is rare, and perhaps not the most important diagnosis for an emergency physician to make. However, if you keep it on your differential diagnosis for patients with cellulitis (febrile patients with tender red rashes), you may help a patient or two in your career, and perhaps even make an early important diagnosis of cancer. 

Some images

References

Cohen PR. Sweet’s syndrome–a comprehensive review of an acute febrile neutrophilic dermatosis. Orphanet J Rare Dis. 2007 Jul 26;2:34. doi: 10.1186/1750-1172-2-34. PMID: 17655751

Korkut M. A dermatologic emergency; Sweet’s syndrome. Am J Emerg Med. 2019 Sep;37(9):1807.e1-1807.e3. doi: 10.1016/j.ajem.2019.06.012. Epub 2019 Jun 5. PMID: 31280940

Pulido-Pérez A, Bergon-Sendin M. Sweet’s Syndrome. N Engl J Med. 2020 Apr 16;382(16):1543. doi: 10.1056/NEJMicm1911025. PMID: 32294348

SWEET RD. AN ACUTE FEBRILE NEUTROPHILIC DERMATOSIS. Br J Dermatol. 1964 Aug-Sep;76:349-56. doi: 10.1111/j.1365-2133.1964.tb14541.x. PMID: 14201182