Birt-Hogg-Dubè (BHD) syndrome is a rare genetic pathology characterized by cutaneous fibrofolliculomas, pulmonary cysts and kidney tumours. Severe asthma is the most serious form of asthma that does not respond to standard treatments. 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 was treated as a severe asthmatic patient for several years with ICS + LABA and high doses of OCS. When we tried to reduce OCS the patient had worsening of the symptoms, we requested a HRTC scan that showed 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. 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 a high percentage of eosinophils, for this reason we opted for the administration of benralizumab that resulted in an excellent asthma control and increased quality of life.