For children, ITP prognosis varies by age, infection status: Study

Older children with immune thrombocytopenia (ITP) who had had an infection tended to achieve sufficient levels of platelets — the cell fragments lost in ITP — to avoid bleeding, as did most children younger than 12, regardless of infection history, a study found.

Fewer older children without an infection achieved this goal.

The findings were detailed in a letter to the editor, “Prognostic significance of age at diagnosis and preceding infection varies across age groups in childhood immune thrombocytopenia,” published in the International Journal of Hematology.

In ITP, the immune system mistakenly attacks healthy platelets, the circulating cell fragments that initiate blood clotting after an injury. The main ITP symptoms are related to an increased risk of internal and external bleeding. The disease can be acute, with platelet levels recovering within a few months, or chronic, persisting in the long term and requiring ongoing ITP treatment. Research shows that ITP is more likely to be acute and self-resolving in children than in adults.

Acute or chronic?

Scientists don’t know exactly what causes the immune system to launch ITP attacks, but in some cases, the disease arises secondarily to an infection or vaccination. It’s thought that these triggers may alter the immune system in ways that make it overly reactive.

An infection or vaccination preceding ITP onset is associated with an increased likelihood that the disease will take an acute course, while the absence of a preceding infection is significantly associated with chronic ITP. While infections in general are a positive prognostic indicator, the scientists have been exploring whether this varies by age group.

In a previous study involving children with ITP, the scientists found that being younger than 3 at the time of ITP diagnosis was associated with a more favorable prognosis. But in these very young children, a preceding infection or vaccination did not further affect outcomes: All had a similar platelet recovery.

“This discrepancy between the overall patient population and younger age groups prompted us to evaluate variables associated with prognosis in different age groups,” the researchers wrote.

The team evaluated the outcomes for different age groups of children diagnosed with ITP after age 3.

Among children who had an infection preceding ITP onset, platelet recovery did not differ between children ages 3-5 and those ages 6-11. There were no children in this group diagnosed at age 12 or older.

On the other hand, platelet recovery differed significantly by age in children who did not have a preceding infection or vaccination. In this group, children diagnosed at age 12 or older had a worse prognosis than younger children. About 30% of those older children achieved a platelet level considered sufficient to prevent significant bleeds, compared with up to 80% of children younger than 12.

Final statistical analyses showed that age at diagnosis was significantly associated with prognosis for all children younger than 3, regardless of vaccination or infection history, and for those ages 3 and older who did not have a preceding infection or vaccination.

“These distinct patterns for age-groups may reflect differences in the underlying pathogenesis [disease mechanisms] of ITP between younger and older children,” the researchers wrote.

Other studies have found that older age at the time of diagnosis is a predictor for the development of chronic ITP in children, according to the scientists.

The researchers speculated that these older children “may exhibit intermediate characteristics suggesting transition to adult-type ITP.”

The fact that no children in the infection group were 12 or older could suggest that maturation of the immune system with age makes older children less susceptible to abnormal infection responses that drive ITP. Still, the exact reasons for these age-related differences are still to be uncovered.

“Further research is needed to determine the underlying pathogenesis of ITP development in children,” the team wrote.