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11 December 2019 - Case of the Month #486

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Thanks to Dr. Patricia Tsang, Geisinger Commonwealth School of Medicine (USA), for contributing this case and Morgan Hrones, medical student-IV, Geisinger Commonwealth School of Medicine (USA) for writing the discussion.





Pathology Practice Opportunity

SUDBURY, ONTARIO (CANADA). Health Sciences North (HSN) is recruiting a full-time general (AP/CP) Pathologist. As the tertiary referral centre for Northeastern Ontario, HSN serves >600,000 residents and hosts the Regional Cancer Centre.

Our department currently includes 11 pathologists providing services to HSN and other hospitals throughout Northeastern Ontario in the following areas: surgical pathology, cytology, hematopathology, flow cytometry, transfusion medicine, forensics, genomics, microbiology, chemistry. The team also includes a Biochemist, Microbiologist and Cytogeneticist.

Candidates should have anatomic and clinical pathology training with skills that complement those of the current group. Specialty training or an interest in neuropathology, genomics and/or laboratory management is an asset.

In addition to service work, pathologists at HSN are encouraged to participate in research at the HSN Research Institute and are required to seek faculty appointments at the Northern Ontario School of Medicine. Most clinical and academic work is completed at the HSN main site, 41 Ramsey Lake Road. Compensation is fee-for-service originating from the Ontario Ministry of Health and Long Term Care and Ontario Health Insurance Plan.

Sudbury offers an exceptional quality of life, with excellent schools, abundant lakes and extensive recreational opportunities and is near Georgian Bay and Muskoka, and a 50 minute flight or 3-4 hour drive from Toronto.

Candidates must be eligible for licensure by the College of Physicians and Surgeons of Ontario (CPSO) and have obtained, or be eligible to obtain, specialty qualifications from the Royal College of Physicians and Surgeons of Canada and/or the American Board of Pathology. CPSO pathway 3 or 4 candidates from the US will be considered.

Interested individuals should send a cover letter and CV to rmcclure@hsnsudbury.ca or to:
Dr. McClure
Department of Pathology
Health Sciences North
41 Ramsey Lake Road
Sudbury, Ontario, P3E 5J1
Canada

HSN thanks all applicants, but only those selected for interview will be contacted.


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Case of the Month #486

Clinical history:
A 43 year old woman with a tick bite while hiking in Connecticut presented to the emergency room with fever, chills and muscle aches.

Giemsa stain images:



What is your diagnosis?

Click here for diagnosis, test question and discussion:



Diagnosis: Anaplasmosis

Test question (answer at the end):
What of the following is true about anaplasmosis?

A. Anaplasmosis is typically transmitted by exposure to respiratory droplets.
B. Immunocompromised patients traveling to endemic regions should be vaccinated against Anaplasma.
C. A common presentation for patients with anaplasmosis includes relapsing fevers, neutrophilia and reactive thrombocytosis.
D. A diagnostic feature of anaplasmosis is the presence of neutrophilic morulae.
E. Anaplasma and malaria are common coinfections.

Discussion:

Human granulocytic anaplasmosis is an emerging tick-borne infectious disease caused by Anaplasma phagocytophilum which is an obligate, intracellular rickettsial bacterium (Infect Dis Clin North Am 2015;29:341). Anaplasma phagocytophilum shares many overlapping clinical characteristics with its closely related relative, Ehrlichia chaffeensis — the causative agent of human monocytic ehrlichiosis (Clin Lab Med 2017;37:317).

In the US, there are approximately 6.3 cases of anaplasmosis infection per million person-years, with the highest prevalence in Minnesota, Wisconsin, Rhode Island and along the coastal New England region (Am J Trop Med Hyg 2015;93:66). Although cases occur year-round, peak incidence tends to occur during the summer months, particularly in June and July (Clin Lab Med 2017;37:317). Anaplasmosis is often underdiagnosed. As with Lyme disease and babesiosis, transmission occurs via the tick Ixodes scapularis in the upper Midwest and northeastern US or through other regional tick species (Clin Lab Med 2017;37:317). Its reservoir mainly consists of small mammals, including the deer and white-footed mouse, and less commonly, larger mammal hosts, such as the white-tailed deer (Am J Trop Med Hyg 2015;93:66).

Although patients are often asymptomatic, severe illness can occur with fever, malaise, headache and chills, typically presenting 7 to 14 days post tick bite (Dis Mon 2018;64:181). Neurologic symptoms and skin rash are infrequent (Infect Dis Clin North Am 2015;29:341).

Diagnostic approach may begin with laboratory studies for sepsis evaluation (e.g., CBC and metabolic panel). Laboratory abnormalities are commonly demonstrated during fulminant illness and include lymphopenia or neutropenia with a left shift (JAMA 2016;315:1767). Although the organism principally infects granulocytes, thrombocytopenia is a characteristic laboratory finding (Am J Trop Med Hyg 2015;93:66). Mild elevations in transaminases are also commonly observed (Clin Lab Med 2010;30:261). Blood culture is typically negative.

Blood smear or buffy coat examination shows the presence of intracytoplasmic inclusions (morulae) in neutrophils. The morulae represent clusters of Anaplasma organisms within the infected granulocytes (Am J Trop Med Hyg 2015;93:66). Serological studies, such as indirect fluorescent antibody staining (IFA) and enzyme-line immunosorbent assays (ELISA), may also be helpful (JAMA 2016;315:1767). The most sensitive detection method is PCR for Anaplasma phagocytophilum DNA (JAMA 2016;315:1767).

Differential diagnoses are vast due to its nonspecific clinical presentation and include human monocytic ehrlichiosis, Rocky Mountain spotted fever, Colorado tick fever, Powasan virus, babesiosis and Lyme disease (Infect Dis Clin North Am 2015;29:341). Other viral etiologies causing hematological abnormalities and a febrile clinical picture can resemble anaplasmosis. These include Epstein-Barr virus, Parvovirus B19, West Nile virus, viral hepatitis and dengue virus (Infect Dis Clin North Am 2015;29:341). Dohle bodies seen in infectious or inflammatory states and neutrophilic green granules seen in severely septic patients can mimic Anaplasma morulae on peripheral blood smear (Vet Clin North Am Small Anim Pract 2007;37:245).

In this case, the blood smear raised the suspicion of Anaplasma and the patient was immediately started on doxycycline. Several days later, PCR for tick-borne illnesses confirmed Anaplasma. After completion of antibiotic treatment, the patient recovered fully.

Test question answer:
D.
Neutrophilic morulae are a characteristic feature of anaplasmosis on peripheral blood smear examination.