According to a study published in the journal Pediatrics, children with acute lymphoblastic leukemia (ALL) are more likely to develop severe chickenpox if they are treated with prednisone shortly before developing chickenpox.
Acute lymphoblastic leukemia (ALL) is a cancer of the bone marrow and lymph system. The bone marrow produces early blood-forming cells called stem cells. These grow and mature into the three blood cell types: white blood cells, which fight infection; red blood cells, which carry oxygen to tissue; and platelets, which help blood to clot. ALL is characterized by uncontrolled production of immature lymphocytes (white blood cells). These immature lymphocytes never develop enough to perform their infection-fighting function. In addition, these rapidly dividing cells crowd and suppress the formation of other important blood cells, such as red blood cells, platelets, and other white blood cells.
Chickenpox is an infectious disease that generally produces a mild illness involving rash, itching, and fever. Some patients, however, become seriously ill. Before the introduction of a vaccine in 1995, chickenpox resulted in 12,000 hospitalizations and 100 deaths each year. Children with leukemia have an increased risk of developing severe chickenpox.
In order to determine whether treating ALL patients with prednisone increases the risk of severe chickenpox, researchers evaluated 697 ALL patients. During follow-up, 110 of these patients (16%) developed chickenpox. The severity of chickenpox was coded on a scale of 1 to 5: Grade 1 chickenpox involved no or minimal symptoms; grade 2 caused mild to moderate symptoms and did not result in hospitalization; grade 3 caused symptoms that required hospitalization; grade 4 involved severe disease with complications or treatment in intensive care; grade 5 resulted in death. In the analysis, grades 1 and 2 were classified as nonsevere and grades 3, 4, and 5 were classified as severe.
Of the 110 chickenpox cases, 56 had nonsevere disease and 54 had severe disease. There were two deaths due to chickenpox. Children who developed chickenpox within three weeks of treatment with prednisone were more likely to develop severe chickenpox:
- Among children who developed chickenpox during the three weeks after prednisone treatment, 70% developed severe chickenpox.
- In contrast, among children who developed chickenpox more than three weeks after prednisone treatment, 44% developed severe chickenpox.
The researchers conclude that chickenpox remains a dangerous illness for children with ALL. Treatment with prednisone during the chickenpox incubation period (the 10-21 days between exposure to chickenpox and development of symptoms) appears to increase the risk of severe chickenpox. The researchers recommend that, when possible, ALL patients who are exposed to chickenpox have steroid treatment delayed until after the chickenpox incubation period has passed.
Reference: Hill G, Chauvenet AR, Lovato J et al. Recent steroid therapy increases severity of varicella infections in children with acute lymphoblastic leukemia. Pediatrics. 2005;116:e525-e529.