Can Anaplasmosis Become Severe? Multiorgan Complications Explained
Severe anaplasmosis can affect multiple organ systems
Older and immunosuppressed patients face a greater risk
Early recognition and doxycycline treatment are essential
Anaplasmosis is often described as an acute tick-borne illness causing fever, chills, headache, muscle aches, and fatigue. However, severe anaplasmosis can lead to confusion, respiratory failure, liver and kidney injury, bleeding disorders, shock, and multiorgan failure.
Most patients improve with appropriate antibiotic treatment, but severe complications can develop rapidly—particularly in older adults, immunocompromised patients, and individuals whose treatment is delayed.
In my experience, most patients with anaplasmosis recover with prompt doxycycline treatment. Nevertheless, severe complications have been described in the medical literature and can occur, particularly in older or immunocompromised patients or when treatment is delayed.
Can anaplasmosis become life-threatening?
Yes. Although many infections are mild or may even go unrecognized, a minority of patients develop serious or life-threatening complications.
Reported complications of severe anaplasmosis include:
- Acute respiratory distress syndrome
- Respiratory failure
- Septic shock-like illness
- Kidney injury or kidney failure
- Liver dysfunction
- Bleeding disorders, including disseminated intravascular coagulation
- Rhabdomyolysis
- Myocardial dysfunction
- Neurologic complications
- Multiorgan failure
Death is uncommon, but it can occur. A Tick-Borne Disease Working Group subcommittee report estimated the case fatality rate for anaplasmosis at approximately 0.3%. Other reviews have reported fatality rates below 1%.
Some patients require intensive care because of respiratory failure, shock, or multiorgan dysfunction.
Who is at greater risk for severe anaplasmosis?
Severe illness is more likely among patients who are older, immunosuppressed, or experiencing delays in diagnosis and treatment.
Risk factors may include:
- Older age
- Immune-suppressing medications
- Cancer treatment
- Organ transplantation
- Chronic medical conditions
- Delayed initiation of doxycycline
- Coinfection with another tick-borne pathogen
Coinfection may complicate diagnosis and contribute to a more severe clinical presentation, although each infection should be evaluated individually.
Because the blacklegged tick can transmit Lyme disease, babesiosis, and anaplasmosis, clinicians may also need to consider tick-borne coinfections when a patient has an unusually severe presentation or does not improve as expected.
Confusion and lethargy were early warning signs
Although uncommon, severe disease is well documented. The following case illustrates how rapidly anaplasmosis can progress in an immunosuppressed patient.
In their case report, “Severe Anaplasmosis With Multiorgan Involvement in a Rheumatoid Arthritis Patient,” Aydin and colleagues describe a 66-year-old woman from Connecticut who was admitted to the emergency department with confusion and lethargy.
The patient was disoriented and had experienced fever, chills, generalized weakness, and poor appetite for two days.
Her medical history included rheumatoid arthritis and hypothyroidism. She was taking immunosuppressive medication for her arthritis.
The woman enjoyed gardening and reportedly discovered several tick bites in her left armpit three days before presenting to the hospital. She did not have a noticeable rash.
“Concerned about her worsening mental status, the husband promptly contacted emergency services,” the authors write.
The absence of a rash did not exclude anaplasmosis. Rash is uncommon with anaplasmosis and, when present, may raise concern for another tick-borne infection or coinfection.
Laboratory findings suggested severe systemic illness
Laboratory testing revealed several abnormalities commonly associated with severe anaplasmosis:
- Pancytopenia, involving reductions in multiple blood cell lines
- Hyponatremia, or a low blood sodium level
- Elevated liver enzymes
- Mild hyperbilirubinemia
- Lactic acidosis
More commonly, patients with anaplasmosis develop leukopenia, thrombocytopenia, and elevated liver enzymes. In severe cases, additional abnormalities may reflect injury to the kidneys, liver, muscles, lungs, or other organs.
PCR testing supported the clinical diagnosis of severe anaplasmosis. PCR can be particularly useful during the early stage of illness, when antibody testing may not yet be positive.
When anaplasmosis is clinically suspected, treatment should not be postponed while awaiting confirmatory testing.
Respiratory failure developed despite prompt treatment
The patient was treated promptly with doxycycline. Nevertheless, her condition initially worsened, and she developed acute hypoxic respiratory failure secondary to acute respiratory distress syndrome.
“As a result of the disease’s progression, the patient developed [acute respiratory distress syndrome] necessitating the use of HFNC therapy to maintain adequate oxygenation.”
High-flow nasal cannula therapy was required to support her oxygen level.
Lung injury in severe anaplasmosis may result from a systemic inflammatory response rather than extensive direct infection of lung tissue. Reported pathologic findings have included interstitial pneumonitis and pulmonary hemorrhage.
Why can anaplasmosis affect multiple organs?
Anaplasma phagocytophilum infects neutrophils, a type of white blood cell involved in the body’s immune response. The organism can interfere with normal neutrophil defenses while stimulating inflammatory signaling.
The severity of illness appears to depend not only on the number of bacteria present but also on the host inflammatory response. Research suggests that an excessive or poorly regulated immune response may contribute to tissue injury.
Inflammatory mediators, including interferon-gamma and interleukin-10, appear to influence the balance between controlling the infection and producing inflammatory damage. This may help explain why some patients develop liver injury, low blood counts, respiratory distress, shock, or multiorgan complications.
A rare but serious complication is hemophagocytic lymphohistiocytosis (HLH), in which excessive immune activation can produce fever, cytopenias, liver abnormalities, high ferritin levels, and organ dysfunction.
Immunosuppression likely increased this patient’s risk
The authors noted that the woman was taking immunosuppressive medications for rheumatoid arthritis. These medications likely contributed to the severity of her illness and the broad range of manifestations affecting multiple organ systems.
Immunosuppressed patients are more likely to require hospitalization and may face a greater risk of serious complications.
The possibility of severe anaplasmosis should therefore be considered when an immunocompromised patient from an endemic area develops an acute illness involving fever, confusion, low blood counts, elevated liver enzymes, or respiratory symptoms—even when no rash is present.
Early treatment remains critical
Doxycycline is the first-line treatment for anaplasmosis. Because severe complications may develop quickly, treatment is generally started when the clinical presentation and exposure history strongly suggest the infection rather than waiting for laboratory confirmation.
“The timely initiation of appropriate treatment, specifically the administration of doxycycline, proved to be crucial in preventing further complications and promoting the patient’s recovery,” the authors state.
The patient eventually recovered with doxycycline and supportive hospital care, despite developing acute respiratory distress syndrome.
The authors conclude that the case highlights the need for healthcare providers to maintain a high index of suspicion, recognize the disease early, and promptly initiate appropriate treatment.
Frequently Asked Questions
Can anaplasmosis become life-threatening?
Yes. A minority of patients develop severe complications such as respiratory failure, shock, kidney injury, bleeding abnormalities, or multiorgan failure. Death is uncommon but possible.
Can anaplasmosis affect the liver?
Yes. Elevated liver enzymes are common in anaplasmosis. Severe infections may produce more significant liver dysfunction, hyperbilirubinemia, or other evidence of organ injury.
Can anaplasmosis cause confusion?
Yes. Confusion, disorientation, lethargy, and encephalopathy can occur, particularly in severe illness. Direct central nervous system involvement is considered uncommon, and altered mental status may also result from systemic infection, low sodium, inflammation, or organ dysfunction. Rare cases of meningoencephalitis and other neurologic complications have also been reported.
Who is most likely to develop severe anaplasmosis?
Older adults, immunocompromised patients, people with significant underlying illnesses, and patients whose treatment is delayed appear to face a higher risk of hospitalization and serious complications.
Should treatment wait for anaplasmosis test results?
No. When anaplasmosis is strongly suspected, doxycycline treatment should generally begin promptly while laboratory confirmation is pending because delayed treatment may increase the risk of severe illness.
Clinical Takeaway
Anaplasmosis may begin with nonspecific symptoms such as fever, chills, weakness, headache, and poor appetite. However, confusion, worsening respiratory symptoms, profound blood-count abnormalities, hypotension, kidney injury, or significant liver abnormalities may indicate severe disease.
Although these severe complications are uncommon in my clinical practice, they have been well described in the medical literature, particularly among older adults, immunocompromised patients, and those with delayed treatment.
Early clinical recognition and prompt doxycycline treatment remain essential to reducing the risk of respiratory failure, multiorgan complications, and death.
Related Articles
Can anaplasmosis cause heart problems?
Anaplasmosis diagnosis: symptoms, testing, and treatment
A confused woman with anaplasmosis and Babesia infection
References
- Aydin Y, Vemuri B, Ahmed SM, Elgamal M, Bilgin S. Severe anaplasmosis with multiorgan involvement in a rheumatoid arthritis patient. Cureus. 2023;15(7):e41536.
- Guzman N, Yarrarapu SNS, Beidas SO. Anaplasma phagocytophilum. StatPearls. Treasure Island, FL: StatPearls Publishing.
- Dumler JS. The biological basis of severe outcomes in Anaplasma phagocytophilum infection. FEMS Immunology & Medical Microbiology. 2012;64(1):13–20.
- Ismail N, McBride JW. Tick-borne emerging infections: Ehrlichiosis and anaplasmosis. Clinics in Laboratory Medicine. 2017;37(2):317–340.
- Dixon DM, Branda JA, Clark SH, et al. Ehrlichiosis and anaplasmosis subcommittee report to the Tick-Borne Disease Working Group. Ticks and Tick-borne Diseases. 2021;12(6):101823.
Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.
Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention
