Red Flags for Human Monocytic Ehrlichiosis in Children?
Schutze GE, Buckingham SC, Marshall GS, et al; for the Tick-borne Infections in Children Study (TICS) Group
Pediatr Infect Dis J. 2007;26:475-479

This article provides description of a large number of human monocytic ehrlichiosis (HME) cases diagnosed over a 13-year period at 6 sites in the United States. The subjects were all 19 years old or younger. Cases were divided into "probable" (some laboratory criteria present plus clinical syndrome compatible with the diagnosis) and "confirmed" (clinical syndrome plus more definitive identification of organism by direct isolation in fluid samples, polymerase chain reaction, immunofluoresce antibody testing, etc.).

The authors first searched administrative records to find diagnoses of rickettsial diseases, then completed in-depth chart reviews. This descriptive study includes data on 32 patients with HME, 14 of whom had confirmed cases. Patients were predominantly male (66%) and white (91%). Sixty-nine percent reported tick exposure. Fever, headache, and myalgias were often present in the confirmed case patients at 100%, 77%, and 77%, respectively.

Patients with probable HME had slightly lower rates of headache and myalgias, at 63% for both. Rash was present in only 57% of confirmed cases but 72% of probable cases (66% overall). Rash was present on the palms or soles in 12.5% of cases (n=4). Abdominal pain was also frequently present at 62% and 69% for confirmed and probable cases, respectively. Finally, nausea and/or vomiting was present in approximately 56% of patients.

On laboratory analyses, small majorities of subjects (~55%) had serum sodium values < 135 mEq/L, and similar percentages had lymphopenia (< 1500/mm) or leukopenia (< 4000/mm). A review of median times to certain events for the subjects reveals much about the natural history of HME.

The median day of first healthcare visit was 1 day after onset of symptoms, with rash onset on day 4 (median). Subjects made a median of 2 outpatient visits before admission to hospital. By day 6, at least half of the subjects had been started on effective antibiotic therapy, and they generally had a resolution of fever by 1 day later.

Median length of hospitalization was 4 days. Almost a quarter of the patients required ICU care. The authors caution that all 3 aspects of the classic triad of rickettsial diseases (fever, headache, and rash) were present together in only 48% of cases.

The authors conclude that diagnoses of HME are often not recognized at initial visit.

The data from this study mainly serve as a reminder of potential "red flags" for placing rickettsial disease on the differential diagnosis list. Fever and headache, especially when rash is present, are the key findings. The palmar and volar rashes, while very helpful diagnostically when present, are usually absent. Season, geographic location, tick exposure (2/3 of these cases), and the overall picture of the patient are likely the best options for picking up ehrlichiosis early.

Abstract