A Case of Severe Allergic Eosinophilic Asthma with Nasal Polyposis in a Patient Affected by Birt-Hogg-Dubé Syndrome Successfully Treated with Benralizumab.

Birt-Hogg-Dube (BHD) syndrome is a rare genetic pathology characterized by cutaneous fibrofolliculomas, pulmonary cysts and kidney tumours (1). Severe asthma is the most serious form of asthma which does not respond to standard treatments (2). We present the case of a 68 years old male patient who had frequent respiratory tract infections, shortness of breath and decline in lung function, nasal polyposis and hypertrophy of the nasal turbinates, for this reason he was treated as a severe asthmatic patient for several years with ICS + LABA and with high doses of OCS. When we tried to reduce OCS, the patient's symptoms worsened, so we requested a HRTC scan that showed the presence of several cysts spread ubiquitously. The patient had a family history of pneumothorax, for this reason we requested a genetic test that resulted in a heterozygous point mutation on exon 12 (c.1429 C > T) of FLCN gene (3). Despite the diagnosis of BHD syndrome, the patient's clinical condition kept on, suggesting an underlying severe asthma and the blood tests we requested pointed out an high percentage of eosinophils. For this reason, we opted for the administration of benralizumab (4, 5) which resulted in an excellent asthma control and in an increased quality of life.