Circulating Blasts in a Crohn’s Patient Treated With Natalizumab

Abstract

### Patient: 34-year-old Caucasian male. ### Chief Complaint: Pathologist’s review of peripheral smear is requested secondary to presence of circulating blasts. ### History of Present Illness: The patient has a 7-year history of Crohn’s disease. He has been treated with Natalizumab (Tysabri) since April 2008, after infliximab and high-dose steroids failed to control his symptoms. He stated he has an average of 5–7 bowel movements daily. He denies changes in the number of bowel movements, hematochezia, abdominal pain, fatigue, night sweats, fever/chills, weight loss, or neurologic symptoms, including visual changes, changes in thought process, or headaches. He also denies recent travel or recent illness. ### Past Medical History: Crohn’s disease diagnosed in 2003, status post partial small bowel resection and multiple stricturoplasties. Well documented iron deficiency anemia. ### Medications: Natalizumab; 300 mg IV every 4 weeks and iron infusions; monthly. ### Family History: Non-contributory. ### Physical Exam: Vital signs: blood pressure, 143/92 mmHg; temperature, 36.1°C; pulse, 81 bpm; respirations, 14. HEENT: Conjunctivae are clear. Sclerae are anicteric. Oropharynx is clear. There is no lymphadenopathy. Abdomen: Active bowel sounds, soft and nontender, no hepatosplenomegaly or masses. ### Principal Laboratory Finding: The laboratory findings at presentation are listed in Table 1. ### Hematopathology Review of Peripheral Blood Smear: Occasional blasts (Image 1) and rare myelocytes present. Adequate platelets; erythrocytes with mild microcytosis, moderate anisocytosis, and polychromasia. 1. What are this patient’s most striking clinical and laboratory findings? 2. What is the differential diagnosis of these findings? 3. What is Natalizumab and what is its therapeutic effect? 4. How does Natalizumab contribute to this patient’s peripheral blood findings? 5. What are Natalizumab’s additional risks? 6. What are Natalizumab’s possible additional applications? 1. The most striking finding in this patient is the presence of circulating immature hematopoietic cells (blasts) in his peripheral smear. The hematology analyzer used in our institution defines the leukocyte differential by flow cytometric principles and staining with myeloperoxidase. In addition to the white cell fractions, the instrument also reports a large unstained cell (LUC) value, relating to populations …