Chronic eosinophilic pneumonia (CEP) is an eosinophilic lung disease, characterized by an history of pneumonia (> 2 months) and eosinophilic pulmonary infiltration without anyorganic causes. CEP is typically diagnosed by a triad of clinical symptoms including pulmonary symptoms, eosinophilia and characteristic radiographic abnormalities. It generally responds rapidly to treatment, which primarily consists of glucocorticoids (GC) therapy, but relapses are common. Mepolizumab (monoclonal anti IL-5 antibody) is one of the biological drugs studied for its efficacy in hypereosinophilic syndromes.

A 49-years-old female with a medical history of eosinophilic asthma and chronic eosinophilic pneumonia in treatment with GC therapy, she reported the appearance of severe dyspnea for about a month and a week of fever, which occurred concomitantly with the reduction of GC. The patient underwent high-resolution chest CT (HRCT), which revealed a picture compatible with an exacerbation of eosinophilic pneumonia.

After the diagnosis of CEP in 2001, the patient was treated continuously with oral GC which  negatively impacted on stabilization of bipolar disorder from which the patient suffers, and also impacted on Cushing's syndrome and metasteroideal diabetes. 

Considering the long history of disease, frequent relapses and secondary complications of GC therapy, off-label therapy with Mepolizumab 100/mg 1 fl subcutaneously per month was also initiated.

During hospitalization and after discharge, we observed a progressive reduction in the eosinophil count in peripheral blood (eosinophils 200/mm3, 1.6%), an improvement of chest CT scan and above all of the patient's overall clinical conditions.

At the endocrinological checkup after the fifth administration of Mepolizumab, there was an improvement of iatrogenic Cushing's syndrome with the appearance of mild hyposurrenalism. Thus, the patient had taken cortisone acetate which led her again to bipolar disorder decompensation.

At the subsequent endocrinological evaluations, after ACTH stimulation test, the patient could finally suspend cortisone acetate, with a consequent global clinical improvement. Also, metasteroideal diabetes treated with insulin went towards a good control (last HbA1c 6%).

The patient has so far continued monthly administrations of Mepolizumab.

To evaluate the use of mepolizumab in chronic eosinophilic pneumonia, focusing on its steroid sparing ability.

Although the drug is off-label for the treatment of CEP, the administration of Mepolizumab in the context of multiple steroid-dependent comorbidities represented a therapeutic choice. The steroid sparing capacity allowed the reduction of daily GC and limited the impact on comorbidities and of other potential side effects.