Beyond hemolysis: redefining pediatric AIHA

In this issue of Blood Advances, Harris et al¹ have identified that pediatric autoimmune hemolytic anemia (AIHA) is much more than an isolated autoimmune cytopenia. In the largest multicenter observational study on pediatric patients with AIHA to date, which included 399 patients, the authors demonstrated that many children have underlying immunological abnormalities that affect the disease course, responsiveness to treatment, and long-term outcomes. Their results strongly support a paradigm change in the understanding of pediatric AIHA from hemolysis itself to an underlying immunological dysfunction and give a compelling rationale for standardized diagnostic evaluation and evidence-based pediatric management guidelines.

Autoimmune hemolytic anemia includes a diverse array of disorders, marked by immune-mediated destruction of red blood cells. The most common subtype in children is warm AIHA (wAIHA), which is largely mediated by immunoglobulin G autoantibodies, whereas cold antibody-mediated syndromes, such as cold agglutinin syndrome and paroxysmal cold hemoglobinuria, depend largely on complement activation and exhibit distinct clinical behavior.² Although these mechanistic differences influence the diagnosis and treatment, they do not account for the remarkable variability in disease severity, recurrence, relapse, or response to therapy observed among children with wAIHA. Likewise, the treatment recommendations for pediatric wAIHA continue to rely largely on corticosteroids and empiric immunosuppression with limited prospective pediatric evidence available to guide second-line therapy. Growing evidence reveals that the disease phenotype, prognosis, and treatment response are driven by the underlying immunological landscape rather than by the autoantibody itself.^3,4

Harris et al elegantly reinforced this concept by demonstrating that pediatric AIHA is frequently the first manifestation of broader immune dysregulation. Evans syndrome was present in 37% of the patients, systemic autoimmune disease in 22% of the patients, and inborn errors of immunity (IEI) in 18% of the patients. Of the 76% of children who underwent a functional immune evaluation, 82% had abnormal functional immune results, and pathogenic genetic variants were detected in nearly one-third of those who were subjected to genetic testing. Importantly, the existence of an infectious trigger did not lower the risk for an underlying IEI, challenging the common assumption that infection-associated AIHA is often a transient, isolated event. These findings imply that rather than marking the completion of the diagnostic evaluation, the diagnosis of AIHA should prompt a comprehensive examination of a broader immune diagnosis.

The study further delineated the clinical features that are linked to worse outcomes. Nearly one-third of children with wAIHA required steroid-sparing therapy during their initial episode, highlighting the limitations of initial corticosteroid-based management. Although 58% of the patients had a single episode of AIHA that resolved, 42% developed recurrent disease with recurrence strongly associated with abnormal immune testing, Evans syndrome, IEI, and other autoimmune disorders. Similar to other recent data, 96% of the patients with cold AIHA had a single episode of AIHA that resolved.⁵ After a median follow-up of nearly 5 years, more than one-quarter of the children with wAIHA remained on active treatment. Perhaps the most sobering observation was that many of the patients who died had a secondary immune diagnosis. Collectively, these findings support a transition from an episode-based approach to one that is centered on risk stratification and multidisciplinary management.

Despite these important advances, several questions remain. The retrospective design and variability in the diagnostic evaluation across participating sites introduced inevitable selection bias. Immunological and genetic tests were neither standardized nor universally performed and were likely preferentially obtained for patients with recurrent or severe disease, Evans syndrome, or a heightened clinical suspicion of a related immune condition. Thus, the true prevalence of IEI and pathogenic variants among all children with AIHA remains uncertain. Similarly, the diverse treatment approaches hindered meaningful comparisons among steroid-sparing therapies. Nevertheless, these limitations do not undermine the central message of the study; instead, they highlight the need for prospective, standardized research.

Perhaps the most important implication of this work is that the current classification of wAIHA, which is based primarily on antibody thermal reactivity, may be inadequate to guide the prognosis and therapy. Future studies should move beyond conventional clinical phenotypes to biologically defined immune endotypes using standardized immune phenotyping, genomic testing, complement profiling, lymphocyte functional analyses, and other multiomic approaches. Such strategies have the potential to identify children at highest risk for recurrence, enhance prognosis, and guide personalized therapy. Equally important, defining the underlying immune defect may facilitate the judicial use of targeted therapies, including sirolimus for autoimmune lymphoproliferative syndrome, abatacept for cytotoxic T-lymphocyte antigen 4 or lipopolysaccharide-responsive beige-like anchor protein deficiency, phosphoinositide 3-kinase (PI3K) inhibitors for activated PI3K syndrome, and potentially complement inhibitors in select patients, thereby moving beyond empiric immunosuppression to precision medicine.^2,6,7

Harris et al have advanced pediatric AIHA beyond the red blood cell. Their study reframes AIHA as a manifestation of an underlying immune disorder instead of a mere antibody-mediated hemolysis and provides a roadmap for future clinical investigations. The challenge now is to translate these observations into standardized diagnostic pathways, multidisciplinary care models, and prospective trials of biology-driven therapeutics. With the growing integration of immune phenotyping and rapid genomic diagnostics in pediatric hematology, the diagnosis of AIHA should no longer mark the end of the diagnostic journey, instead, it should mark its beginning.

Conflict-of-interest disclosure: The authors declare no competing financial interests.