A patient with acute myelogenous leukemia (AML) recently presented with what was thought to simply be a swollen left elbow. The patient underwent a standard workup for septic arthritis, including arthrocentesis, negative cultures, and empiric antibiotic treatment. The patient’s elbow subjectively improved and the cultures of the elbow were repeatedly negative for both bacteria as well as crystals, so antibiotics were discontinued. Several days after reporting increased range of motion, the patient suddenly developed diffuse joint pain, fever, and mild conjunctivitis. This unusual and unexpected reaction lead to the discussion of how one key finding was missing in order to make the presumed diagnosis of a rare condition: Sweet syndrome.

Sweet syndrome was first described by Dr. Robert Sweet in 1964 as acute febrile neutrophilic dermatosis. The condition is relatively rare, and its pathophysiology is not exactly understood. However, the pathophysiology likely includes a dysregulation in the T-cell and neutrophil activation within the immune system. Up to 25% of patients with Sweet syndrome have an underlying malignancy, with hematological malignancies (such as acute myeloid leukemia and myelodysplastic syndrome) more commonly implicated compared with solid tumors. Women are more affected than men, and the diagnosis is often preceded by a history of upper respiratory tract infection.

The syndrome itself is characterized by new onset of fever, occasional ocular involvement (including conjunctivitis), rash containing red papules and plaques, and arthralgias and myalgias involving mostly the wrists and knees. The dermatological findings that were missing in our patient included the red to purple, painful plaques that often contain blisters and are target-shaped. Patients with Sweet syndrome typically have an erythrocyte sedimentation rate (ESR) above 20 mm/hr, elevated C-reactive protein level, and neutrophils (including bands). However, these are relatively nonspecific findings and are commonly increased in patients both with and without an underlying malignancy. The diagnosis of Sweet syndrome can be aided by a skin biopsy, which typically shows a dense neutrophilic infiltration without any direct vasculitis. These patients typically respond well to glucocorticoids and have no response to antibiotics.

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Although our patient did not appear to have the unique diagnosis of Sweet syndrome due to the lack of dermatological findings, this case serves as a reminder that cancer patients with any new complaint should be worked up for a potentially broader differential diagnosis. Our patient actually had the preliminary diagnosis of new onset rheumatoid arthritis due to an elevated rheumatoid factor, subjective response to steroids and other labs pending. As many health care professionals are trained to recognize that “common things happen commonly”, there should have been a low threshold in considering the “zebras” of the world such as Sweet syndrome or any other unique diagnoses that may occur in cancer patients.

Questions to Readers

  • What types of patients (AML, MDS, etc) have you seen Sweet syndrome in?
  • Besides the dermatological exam, were there any other key subjective or objective findings that contributed to your diagnosis?

Readers: We’d love to hear from you in the comments section below! If you have a case study or a more extended response to this subject, click here to submit an item for us to publish