Allergic bronchopulmonary aspergillosis with normal serum IgE in a child with cystic fibrosis

Diagnostic criteria for allergic bronchopulmonary aspergillosis (ABPA) in patients with cystic fibrosis have required an absolute increase in total serum immunoglobulin E (IgE) to >1000 IU/mL (2400 ng/mL). Current guidelines recommend in depth evaluation for those with IgE >500 IU/mL (1200 ng/mL), or even for those with lower values if there is clinical suspicion for ABPA. We present a case of a patient who met all criteria for ABPA with the exception of elevation of IgE above the diagnostic level. An increase in serum IgE from the baseline level, but not >1000 IU/mL, and subsequent return to baseline corresponded to a clinical exacerbation and resolution of presumptive ABPA.