A case of Sweet syndrome associated with human granulocytic anaplasmosis.

Background: Acute febrile neutrophilic dermatosis, or Sweet syndrome (SS), is a condition that is presumed to be triggered by infectious disease agents. We report a case of SS associated with human granulocytic anaplasmosis (HGA), which is of interest because Anaplasma phagocytophilum infects, multiplies in, and disrupts the function of neutrophils, the key infiltrating cell in SS.
Observations: A patient with initial dermatologic manifestations of SS who did not respond to standard SS treatment was suspected to have concurrent HGA with the demonstration of leukopenia, thrombocytopenia, and elevated hepatic transaminase levels. The HGA diagnosis was established when morulae in neutrophils were observed on a peripheral blood smear, a finding confirmed by both serologic examination and polymerase chain reaction on the skin biopsy specimen used to establish the SS diagnosis.
Conclusion: The significant involvement of neutrophils with both SS and HGA warrants a broader search for additional cases that may further define whether pathogenetic linkages could exist.