You have recieved your COVID19 immunizations and have returned to your in-patient
and out-patient medical practice.
Your patient is a 64-year-old woman from New England with a past history of relapsing-remitting
multiple sclerosis who was referred to you because of intermittent nausea and fatigue
of seven months duration. A CT scan of her abdomen done 5 months before your exam
revealed cholelithiasis and splenomegaly and blood work done at that time revealed
a normochromic normocytic anemia and thrombocytopenia with a hemoglobin of 8.3 g/dl,
a hematocrit of 26.1%, and a platelet count of 95,000 per uL. Her reticulocyte count
was 4.6%, ferritin 1,248 ug/L, CRP 144.7 mg/L, and haptoglobin <14 mg/dL.
Her symptoms and laboratory abnormalities had failed to respond to an empirical
course of prednisone and she developed intermittet fever with worsening of her nausea
and fatigue.
Your exam reveals a chronically ill appearing woman with a temperature of 38.3°C,
a BP of 90/54 mm Hg, a respiratory rate of 19 breaths per minute and a regular pulse
rate of 93 beats per minute. Her BMI is 32.2. Positive findings include conjunctival
pallor, splenomegaly, and leg edema.
The results of a contrast enhanced CT scan and a 18F-fluorodeoxyglucose scan of the chest, abdomen and pelvis are shown in panels A and
B below, respectively.
What is your diagnosis, what test(s) would you order to confirm your suspicions,
and what treatment, if any, do you recommend?
Diagnosis: Hemolytic anemia. The constellation of a low haptoglobin level, an elevated
reticulocyte count, and a positive test for urobilinogen in the absence of hyperbilirubinemia
is a pattern consistent with hemolytic anemia. In fact, a haptoglobulin level of less
than 25 mg/dL is 96% specific for hemolysis.
Disorders inherent to the red cell structure (enzymopathy, membranopathy, and
hemoglobinopathy) would be expected to have presented early in life, and conditions
that result from mechanical injury (e.g., aortic stenosis, the presence of mechanical
prosthetic heart valves or a microangiopathic hemolytic anemia) are inconsistent with
the patient's history. In addition, a direct Coombs' test is negative, mediating against
an immune mediated hemolytic anemia. A clue to the definitive diagnosis in this case
is provided in the figure below.
DIAGNOSIS: Babesiosis. Babesia microti, which is carried by the deer tick Ixodes scapularis, is endemic to the northeastern United States. Infection with this organism causes
direct hemolysis as well as immune-mediated hemolysis by splenic macrophages due to
the presence of babesial antigen on red cell surfaces.
Patients with babesiosis typically present with an acute illness characterized
by fever, fatigue, gastrointestinal symptoms, splenomegaly, and a Coombs' negative
hemolytic anemia. The disease is more fulminant in patients who are splenectomized
or on immunosuppressive therapy. Infection with this organisms can lead to the development
of hemophagocytic lymphohistiocytosis (HLH)
The diagnosis of babesiosis is established by examining thick and thin blood
smears (see above) and/or by performing babesia-specific nucleic acid testing of the
blood.
The patient was treated for 12 weeks with azithromycin and atovaquone with complete
resolution of her parasitemia.