Eosinophilic granulomatosis with polyangiitis (EGPA), previously called Churg—Strauss syndrome, represents a rare form of ANCA-associated necrotising vasculitis which affects small vessels. This disease is characterized by typical combination of immunological disturbances, hypereosinophilia, severe bronchial asthma, transient pulmonary infiltrates, and kidney injury which is less frequent than in other forms of necrotising vasculitis.Verification of the diagnosis is often hampered by comorbidities, such as chronic obstructive pulmonary disease (COPD) in the patients with long-term smoking history and occupational hazards.In this article, we report a clinical case of EGPA in elderly patient with preceding COPD which caused diagnostic difficulties for this eosinophilic syndrome. Clinical pattern at the beginning of disease was presented by moderate inspiratory dyspnea and cough with small amounts of mucus sputum, which appeared after longterm exposure to chlorine-containing substances. COPD diagnosis in this patient was based on clinical pattern, long smoking experience, and occupational hazards. However, persistence of the symptoms during the ongoing therapy, as well as multidirectional dynamics of transient pulmonary infiltrates found on repeated CT-scans, prompted us to intensify diagnostic search for a systemic disease. Clinical, laboratory and instrumental signs of bronchial asthma were revealed, as well as hypereosinophilia and sensory polyneuropathy, which, if combined with CT-scan data, allowed us to prove the EGPA diagnosis.This case shows that, despite great value of immune diagnostics, with negative blood tests for ANCA, it is necessary to detect mutually complicating comorbid pathology. EGPA was considered the basic diagnosis, and COPD as accompanying disorder, taking into account such reasons as an unfavorable prognosis for EGPA and the need for long-term chemotherapy with systemic corticosteroids and monoclonal antibodies. ANCA-negative testing in the patient, absence of severe kidney and skin lesions allows to suggest better clinical prognosis in this patient.
