Atypical Presentation of Cutaneous Tularemia
By Matthew Watson, June 27, 2008
In an article published in the July 1, 2008 issue of Clinical Infectious Disease, Byington and colleagues describe cutaneous tularemia in two children who were initially misdiagnosed due to atypical presentations of the disease.1 Cutaneous tularemia can present with vesicular lesions on the skin, instead of the more typical suppurative lesions, and clinicians should be aware of this to ensure that optimal treatment is initiated in a timely manner. (See authors’ photographs in original article.)
Background Information on Tularemia
Tularemia is a zoonotic disease caused by Francisella tularensis, a gram-negative coccobacillus. The primary natural reservoir is a number of small mammals, including voles, mice, water rats, squirrels, rabbits, and hares. Human infection occurs in several ways: through bites of infected arthropods; by handling infectious animal tissues or fluids; through direct contact with or ingestion of contaminated food, water, or soil; or by inhaling infective aerosols.2 Manifestation of clinical disease, which may take several clinically distinct forms, typically takes place within 3 to 5 days post exposure, depending on the mode of transmission.
Ulceroglandular (cutaneous) tularemia is acquired by direct contact with infected animals or through bites from an insect vector (e.g. ticks, biting flies) and presents with cutaneous lesions, typically ulcers. In contrast, pneumonic tularemia is acquired through inhalation of the aerosolized bacterium, and is the presentation expected to follow a bioterrorist event.2 (See Tularemia Agent Fact Sheet.)
Though tularemia is endemic to the United States, its incidence is low: fewer than 200 new cases are reported to the Centers for Disease Control and Prevention (CDC) annually.3 Since clinicians do not, for the most part, have experience with evaluating and diagnosing cases of tularemia, it may not be included in the formulation of a differential diagnosis.
2 Cases of Atypical Presentation in Children
The authors describe the atypical presentation of cutaneous tularemia in two children. The first, a 6-week old infant, presented with fever and vesicular lesions on the foot, and was initially diagnosed with herpes simplex virus (HSV). The second patient, a ten year old who presented with fever and vesicular lesions on the face and extremities, was initially diagnosed with varicella zoster virus (VZV). In both cases, a history of insect bites was elicited during interview. Similarly, both cases were diagnosed with tularemia after blood and vesicular cultures yielded F. tularensis. Both patients recovered uneventfully after antimicrobial treatment was initiated.1
The authors conclude that F. tularensis infection in patients who present with vesicular lesions can be easy to misdiagnose as more common conditions, such as HSV or VZV. Diagnosis on the basis of visual inspection alone is especially misleading. A complete history should be obtained to elicit potential risk factors such as insect bites or outdoor activity. Appropriate microbiological studies should likewise be obtained to identify accurately the causative agent and ensure initiation of appropriate treatment in a timely fashion.2
Byington CL, Bender JM, Ampofo K et al. Tularemia with Vesicular Skin Lesions May Be Mistaken for Infection with Herpes Virus. Clin Infect Dis. 2008;47:e4.
Dennis DT, Inglesby TV, Henderson DA, et al., Tularemia as a Biological Weapon: Medical and Public Health Management. JAMA. 2001;285:2763-2773.
Hayes EB, Marshal S, Dennis DT et al. Tularemia – United States - 1990 -2000. MMWR. 2002;51:181-184.