This unknown case tests your ability to interpret cells on a blood smear.If you want to test yourself with other unknown cases, here are some to try:

  • Case 1: 20-year-old male who died suddenly
  • Case 2: 72-year-old male with right calf mass
  • Case 3: 67-year-old female with pancytopenia
  • Case 4: 59-year-old male with severe headaches
  • Case 5: 38-year-old female with deep venous thrombi
  • Case 6: 13-year-old male with cerebellar mass
  • Case 7: 45-year-old male with pulmonary emphysema
  • Case 8: 38-year-old male with AIDS and headaches
  • Case 9: 25-year-old male with arm mass
  • Case 10: 57-year-old male with fatigue and left upper quadrant heaviness

Back to this case. Take a look at the photo and the question, then scroll down for the answer.


A 62-year-old male presents with hepatosplenomegaly, skin lesions, and cardiomyopathy. A representative field of his blood smear is shown here. Of the following, which is the most likely diagnosis?

A. Multiple myeloma
B. Chronic myeloid leukemia
C. Metastatic prostate carcinoma
D. Hypereosinophilic syndrome
E. Bacterial sepsis


(Scroll down for the answer)





The diagnosis in this case is hypereosinophilic syndrome, a rare myeloproliferative disorder characterized by a marked and persistent elevation in the eosinophil count. Multiple organs are usually affected, and patients may present with cardiomyopathy, skin lesions, thromboembolic disease, neuropathy, hepatosplenomegaly, or pulmonary disease. The pathophysiology behind the damage in these organs isn’t well understood, but it probably has something to do with the release of eosinophil granules in those tissues.

You need to have three things in order to make the diagnosis:

  1. Eosinophilia (absolute eosinophil count >1500/μL)
  2. No other cause for the eosinophilia
  3. Signs and symptoms of organ involvement

Other more common causes of eosinophilia, such as drug reactions, autoimmune disease, infection, hematologic malignancy, and familial eosinophilia, must be ruled out before making the diagnosis.

Usually, patients aren’t treated unless or until they have symptoms (because the treatment itself has its risks). These patients are monitored closely with serum troponin levels (to monitor for MI), echocardiograms and pulmonary function tests.

Some patients with hypereosinophilic syndrome have a tiny deletion in 4q12, which ends up producing a fusion transcript called FIP1LI-PDGFRA (which is also present in some cases of systemic mastocytosis). Imatinib works very well in the majority of these patients.

Patients who have symptoms (but not FIP1LI-PDGFRA) are generally treated with steroids first. If those don’t work, interferon alpha and hydroxyurea are used. If those don’t work either, then imatinib is the treatment of choice (it doesn’t work as well as it does in patients with FIP1LI-PDGFRA, but it does seem to work in at least some of these patients).