Pneumocystis jirovecii pneumonia (PCP) is a relatively rare complication in non-HIV patients receiving immunosuppressive treatment. Since the introduction of tumour necrosis factor-α inhibitors cases of this complication have increased. We report the case of a 54-year-old, HIV-negative patient, who presented to our department with a long history of pustular psoriasis with poor response to traditional treatments. During the last admission he developed a severe flare that was unresponsive to cyclosporine, therefore infliximab was initiated. After the third dose he developed PCP that required admission to the intensive care unit, with a positive response to i.v. administration of trimethoprim/sulfamethoxazole. During follow up a mutation in the IL36RN gene compatible with an IL-36RN deficiency was found and anakinra was started, with rapid improvement of his psoriasis. PCP is a severe complication in patients receiving immunosuppressive therapy and is probably underreported by dermatologists. There are no clinical guidelines for PCP prophylaxis in dermatological patients who will receive immunosuppressive or biological treatments. We believe that it is necessary to report the cases of PCP to assess the real impact of this complication and develop appropriate prophylaxis guidelines.