RESUMEN
BACKGROUND: Hypereosinophilic syndrome (HES) is defined as an eosinophil count equal to or greater than 1.5 G/L for more than 6 months with organ damage (heart, nervous system, lung, etc) after the exclusion of other common causes of eosinophilia. A myeloproliferative variant of HES with FIP1L1-PDGFRα fusion gene inducing constitutive activation of a tyrosine kinase receptor has been characterized. We report a case in which the diagnosis was revealed by mucosal erosions and ulcerations. PATIENTS AND METHODS: A 50-year-old man reported bipolar erosions. He presented with an erosion on the glans, an ulceration on the lower lip and mild dermographism. He had an eosinophil count of 7.5 G/L (n<0.7) and raised LDH at 520 IU/L (n<480). Screening for the usual causes of eosinophilia was negative. Histology of the labial ulceration showed a polymorphous inflammatory infiltrate containing eosinophils. A chest scan demonstrated a ground glass-like pulmonary infiltrate and broncho-alveolar lavage revealed eosinophilic alveolitis. The myelogram showed rich bone marrow with eosinophils. FIP1L1-PDGFRα fusion transcript was detected in the blood. Imatinib (Glivec(®)) was initiated and a favourable outcome was achieved within a few months and maintained after one year of treatment. DISCUSSION: Cutaneous signs are frequent features of HES. They are polymorphous and include pruritis, erythematous rash and urticaria. Mucosal ulcerations are uncommon and appear more frequently with the myeloproliferative FIP1L1-PDGFRα-associated variant of HES. Early diagnosis allows the onset of a targeted treatment with imatinib that may prevent the apparition of organ damage.