The function of eosinophils in ALHE is poorly understood; it is unclear whether they act as a primary driver of pathogenesis or are simply indicators of secondary infiltration or infection. Our review of the current literature suggests that eosinophils are unnecessary for progression of ALHE but might be involved at its onset. As reported, even monoclonal antibody therapy (eg, mepolizumab and benralizumab) that effectively depletes eosinophil levels by negating IL-5 signaling do not slow progression of ALHE.11 Symptomatic changes are modest at best (ie, simply softening the ALHE nodules).
Our patient had no peripheral eosinophilia, suggesting that the onset of ALHE might not be caused by eosinophilia but a different inflammatory process—in this patient, by CM. Because peripheral eosinophilia was not seen in our patient, the presence of eosinophils in the ALHE lesion likely is unnecessary for its onset or progression but is a secondary process that exacerbates the lesion. The pathogenesis is unknown but could be directed toward lymphocytes and plasma cells, with eosinophils as part of the dynamic process.11
Conclusion
Because reports of an association between CM and ALHE are limited, our case is distinguished by a unique clinical presentation of ALHE. When a patient is given a diagnosis of ALHE, it therefore is important to consider exposure to CM as a cause, especially in patients who reside in or travel to a region where CM is endemic.