Falsely elevated immunologic markers with erythema nodosum and arrythmias in the setting of Q Fever

Abstract

This work describes a case of a young adult male who presented with a fever of unknown origin of several weeks’ duration and a painful, palpable rash. Initial workup suggested a viral or immunologic cause of his symptoms, as both rheumatoid factor and CMV antibodies (IgM and IgG) were positive. Repeat testing one week later was negative for CMV antibodies, and send-off testing eventually confirmed a diagnosis of Q fever. Biopsy of a skin lesion showed panniculitis consistent with erythema nodosum, an exceedingly rare manifestation of Q fever. The patient also experienced cardiac arrythmias during his hospital stay, although no structural heart disease was noted on imaging. The severity and duration of this patient’s symptoms were unusual for Q fever, particularly as they presented in an otherwise healthy young male. His positive rheumatoid factor and CMV antibodies were likely a result of immunologic activation in response to the Q fever infection. Falsely elevated immunologic markers may delay the diagnosis and treatment of Q fever—especially when combined with signs such as erythema nodosum that are more commonly associated with other immunologic or infectious etiologies. As a result, this case serves as an important reminder to consider immunologic overlap when test results are inconsistent and when the patient may have experienced direct or indirect animal exposure.

Key Words

Q Fever, Coxiella burnetii, erythema nodosum, myocarditis, endocarditis, immunologic overlap, immunologic arousal, immunologic activation