Hypereosinophilic Syndrome of Undetermined Significance – Difficulties in Clinical and Therapeutic Approach

We report a case of a 69-year-old woman who is followed since seven years for persistent blood hypereosinophilia up to 5100/mmc. She has been extensively investigated for other diseases known to induce hypereosinophilia, including allergies, parasitic infections and neoplasia. No end-organ dysfunction could be confirmed. We considered a possible primary hypereosinophilic syndrome (HES) and determined the genetic mutation FIP1L1-PDGFRA characteristic for HES, which was negative.

Bone marrow showed reactive eosinophilia with no malignant cells and rare mast cells, less than 15 in aggregates, which is the major criterion for diagnosing mastocytosis. Knowing the association between HES and mastocytosis, we measured and found high serum tryptase levels and positive c-kit D816V genetic mutation, characteristic for systemic mastocytosis. The patient was closely monitored, with regular hematologic and clinical evaluation, mainly for cardiac and neurologic manifestations.

A short trial of high dose corticotherapy induced remission of hypereosinophilia, but this could not be maintained with lower doses. The clinical outcome during follow-up period was rather good, except mild cognitive decline and atrial fibrillation.The reported case is illustrative for versatile presentation and difficulties in management of hypereosinophilia in clinical practice.