Israel Medical Association Journal

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening disorder of immune dysregulation characterized by an inadequate attenuation of the cytotoxic and innate immune system resulting in uncontrolled inflammation in multiple organ systems. Predominant clinical findings include fever, cytopenia, and hepatosplenomegaly [1].

Infectious diseases are a well-documented trigger of HLH, with viral infection being the most common cause. Less commonly, HLH has also been reported in the setting of bacterial infections, with rare cases described secondary to rickettsial diseases [1]. In this report, we present a case of HLH in the setting of bacterial infection with Rickettsia typhi, murine typhus.

Background: We treated two patients diagnosed with legionellosis and simultaneous Rickettsia conorii co-infection.

Objectives: To report the clinical and laboratory characteristics of this unusual combination, and to describe the execution and results of our environmental and epidemiologic investigations.

Methods: Serial serologic testing was conducted 1, 4 and 7 weeks after initial presentation. Water samples from the patients’ residence were cultured for Legionella. Follow-up cultures were taken from identical points at 2 weeks and at 3 months after the initial survey.

Results: Both patients initially expressed a non-specific rise in anti-Legionella immunoglobulin M titers to multiple serotypes. By week 4 a definite pattern of specifically elevated IgG[1] titers became apparent, with patient 1 demonstrating a rise in specific anti-L. pneumophila 12 IgG titer, and patient 2 an identical response to L. jordanis. At 4 weeks both patients were positive for both IgM and IgG anti-R. conorii antibodies at a titer ³ 1:100. Heavy growth of Legionella was found in water sampled from the shower heads in the rooms of both patients. Indirect immunofluorescence of water cultures was positive for L. pneumophila 12 and for L. jordanis.

Conclusions: Although most cases of community-acquired Legionella pneumonia in our region appear simultaneously with at least one other causative agent, co-infection with R. conorii is unusual and has not been reported to date. This report illustrates the importance of cooperation between clinicians and public health practitioners.