Human monocytic ehrlichiosis (HME) can be a life threatening illness and requires a high index of suspicion for early diagnosis. It is caused by Ehrlichia chaffeensis and principally transmitted by the Lone Star Tick (Amblyomma americanum). We report a case of severe acute HME complicated by septic shock, adult respiratory distress syndrome (ARDS), and disseminated intravascular coagulation (DIC) associated with trimethoprim-sulfamethoxazole (TMP-SMX) therapy.
A 19 year old white female with past medical history notable for frequent episodes of sinusitis was in her usual state of health until two weeks prior to admission when she developed rhinorrhea, headache, and fever. One week prior to admission she was diagnosed with sinusitis and treated with TMP-SMX. Symptoms continued to progress until one day prior to admission she developed nausea, vomiting, stiff neck, and malaise and was admitted to an outside facility. She attended college in Chapel Hill, NC and was on the national swim team, but presented in Florida on summer vacation. She had no known history of tick exposure. Pertinent exam findings included fever, tachycardia, decreased level of arousal, meningismus, diffuse muscle tenderness, hepatosplenomegaly, and the absence of rash. Laboratory evaluation was notable for pancytopenia with a left shift, mild azotemia, and elevated liver tests. A non-contrast head CT was unremarkable, and CSF examination revealed a monocytosis with elevated protein and a normal opening pressure. She was treated with vancomycin, ceftriaxone, doxycycline, and acyclovir and transferred to our facility. Review of prior CSF sample revealed monocytes with intraleukocytic morulae, diagnostic of HME (Figure 1). Bone marrow aspirates revealed similar findings (Figure 2). Titers for Ehrlichia chaffeensis were markedly elevated. Antibiotics were continued, however her course was complicated by ARDS, DIC, and multi-organ failure. She died despite maximal supportive efforts. Post-mortem examination revealed findings consistent with septic shock and DIC.
The acute form of HME caries an overall mortality rate of 2-5%. Clinical features include a non-specific illness characterized by fever, malaise, myalgia, nausea, and vomiting. Lab abnormalities are prominent and include leukopenia, thrombocytopenia, elevated transaminases, and elevated lactate dehydrogenase (LDH). The differential diagnosis includes Rocky Mountain spotted fever, meningococcemia, viral illnesses (including acute mononucleosis and hepatitis A), hematological malignancy, and thrombotic thrombocytopenic purpura. Prompt diagnosis is critical, as delayed treatment with doxycycline or chloramphenicol results in increased morbidity and mortality (1). Treatment of HME with TMP-SMX has been reported to worsen the course the disease by an unknown mechanism, and was associated with ARDS and DIC in a case report (2). The association of TMP-SMX with ARDS has been previously reported with rickettsial infections and has also been shown to worsen Mediterranean spotted fever, illnesses caused by organisms closely related to ehrlichia species (3).
Acute HME is a severe life threatening illness that mimics multiple other diseases. The diagnosis requires a high index of suspicion and treatment with doxycycline or chloramphenicol should be initiated early. Treatment with TMP-SMX appears to worsen outcomes due to an association with ARDS and DIC.
S.M. Rowe, None.