Anaphylaxis, the most severe form of an allergic reaction, is a potentially life-threatening systemic reaction requiring prompt and effective management. A subset of cases shows a recurrence of symptoms despite adequate care and full clinical response. These biphasic or even multiphasic courses provide a unique challenge for clinicians, especially as reported incidence varies, risk factors are unclear and clear management strategies are lacking in current guidelines. This is especially true for multiphasic anaphylaxis presenting with multiple relapses into anaphylaxis despite adequate response to standard treatment with epinephrine. Due to the relatively rare occurrence of multiphasic anaphylaxis, case reports providing examples of clinical management can provide an important source of insight into this clinical problem. In this study, we present the case of a woman in her 60s presenting with multiphasic anaphylaxis to clarithromycin, with subsequent analysis showing a high likelihood of systemic mastocytosis, though she did not meet formal diagnostic criteria.
Schneider et al. (2026) studied this question.