A rare case of long-term immune depletion in children following chemotherapy for acute leukemia: secondary or primary immunodeficiency?

Case presentation
A 12-yo girl was diagnosed at the age of 3 (2014) with acute lymphoblastic leukemia (ALL) and treated with chemotherapy for 2 years resulting in transient symptomatic hypogammaglobulinemia. No B-cell depleting anti-CD20 therapies were prescribed. To date, the patient is in complete remission.
In 2017, she developed a new hypogammaglobulinemia associated with a low vaccine response. Immunoglobulin replacement therapy (IgRT) was initiated. The patient developed adverse events (fever, chills) to several Ig preparations until she was switched to Iqymune®, which was well tolerated.
Repeated IgRT discontinuation attempts failed. Exploration revealed a low rate of Memory B cells and Class-switched Memory B cells. These rates remained almost unchanged even 5 years after the end of chemotherapy. Genetic investigation didn’t exhibit any genetic mutation. There was no family history of immune deficiency.
To date, the patient is still treated with a monthly infusion of Iqymune® at 0.4g/kg. No infections were recorded during this treatment. Discussion In this case, the etiology of immunodeficiency is not well established. Knowing that chemotherapy is aggressive with risk of mutation, and that a treatment is usually administered before the immune system reaches its maturity (7-8 years of life), a mutation leading to immunodeficiency could not be ruled out. This hypogammaglobulinemia may also be an infra-clinic primary immune deficiency revealed after the chemotherapy. Epigenetic changes leading to delayed or silenced maturation of B cell function may also be hypothesized.
Fever, and chills are frequent in pediatric ALL patients and are related to IgA levels. The low rate of IgA within Iqymune® could explain the good tolerance in this patient.
It could be difficult to discern between primary and secondary immune deficiencies due to crossover between the two entities. Iqymune® displayed a better tolerability profile compared to previous Ig preparations in this patient.

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