Desensitization to an isatuximab allergy in patients with indolent systemic mastocytosis (SM) appears possible, according to a recently published letter to the editor in the Journal of Investigational Allergology and Clinical Immunology.
Isatuximab is a monoclonal antibody intended to treat adults with multiple myeloma. Multiple myeloma can coexist with other hematologic disorders, such as SM. There are reports of patients with indolent SMIndolent SM A subtype of nonadvanced SM caused by the abnormal accumulation of mast cells in the bone marrow and other organs. Indolent SM accounts for around 90% of SM cases. and concomitant multiple myeloma who developed a strong allergic reaction (anaphylaxisAnaphylaxis A severe allergic reaction that can turn fatal without treatment. Patients with SM are at a higher risk of developing anaphylaxis.) towards isatuximab with marked mast cell activationMast cell activation Describes when mast cells release histamine and other mediators into the blood stream in response to an allergen or other trigger. This leads to symptoms like fatigue, rash and, in severe cases, anaphylaxis.. Anaphylaxis involves an excessive immune response from the organism that can lead to airway obstruction, hypotension, shock, and death.
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The authors suggest that desensitization, the process by which the immune system stops reacting against a given antigen, is possible in such patients.
The case involved a 52-year-old woman with multiple myeloma and a history of indolent systemic mastocytosisMastocytosis Rare disease caused by the buildup of mast cells. Cutaneous mastocytosis primarily affects the skin and is more common in children, while systemic mastocytosis affects internal organs and is more common in adults. (ISM). The patient needed to take antihistaminesAntihistamines Medications that block the effects of histamine, the chemical found in mast cells that is responsible for many of the symptoms of SM, as well as many allergic reactions. daily to prevent SM-associated symptoms such as flushing and palpitations.
As part of her treatment for multiple myeloma previous to bone marrow transplantation, the patient received isatuximab for 10 days without eventuality. Six months later, the patient received isatuximab once again, developing anaphylaxis symptoms within 15 minutes. Treatment was immediately interrupted, and the patient was stabilized with intravenous steroids.
One year after the episode, the patient presented with a multiple myeloma relapse that required isatuximab treatment. Therefore, the attending physicians developed a desensitization schedule that involved administering 12 small, escalating doses together with an immunosuppressant (dexamethasone), in the course of a day. After four days of desensitization treatment, the patient was able to resume her multiple myeloma treatment without complications.
“This is the second report of RDD to isatuximab,” the authors wrote.” We describe a slightly different but equally successful procedure in a patient with underlying [SM] and previous severe anaphylaxis as additional risk factors.”
