The aim of this study was to investigate the clinical characteristics, diagnosis and treatment of
anti-neutrophil cytoplasmic antibody (
ANCA)-negative
microscopic polyangiitis (MPA). We described the case of a patient with
ANCA-negative MPA and conducted analyses and a review of the relevant literature. Based on the collected data, the epidemiology, diagnosis and treatment of
ANCA-negative MPA were discussed. The patient, a 69-year-old male, was initially diagnosed with
pneumonia and
interstitial lung disease (ILD) based on his clinical symptoms. The patient was
ANCA-negative. The follow-up and consultations with the relevant departments after the
ANCA testing led to a diagnosis of MPA being considered. The administration of
glucocorticoids and
immunosuppressant drugs was found to improve the symptoms of the patient. The clinical symptoms of MPA are unspecific. The majority of MPA cases are
ANCA-positive, but misdiagnosis should be considered as a possibility in
ANCA-negative cases. When patients are suspected to have MPA, therefore,
ANCA tests should be immediately performed. Test results should be analyzed for the early diagnosis of MPA in order to enable the provision of immediate treatment, improve patient prognosis and reduce mortality rate.