Uncommon onset manifestations without renal involvement in microscopic polyangiitis: A case report

Microscopic polyangiitis (MPA) is a rare, idiopathic, autoimmune, systemic disease that most frequently involves the kidneys. The present study reports the case of a 48-year-old female patient who presented with diffuse myalgia, arthralgia of both hands and feet for 2 weeks before being admitted to the hospital. The patient exhibited involuntary loss of weight and occasional slight fever. Physical examination noted microstomia and perioral radial furrows, slight skin induration of the hands, discrete cyanotic skin areas on the dorsal side of both feet. The patient also presented bilateral crepitant rales. Laboratory findings at admission revealed non-specific biological inflammatory syndrome consisting of high erythrocyte sedimentation rate and high C-reactive protein. The patient was initially suspected of systemic sclerosis due to the appearance of microstomia and the slight skin induration of the hands with diffuse arthralgia and myalgia, although with negative immune tests (anti-SCL70 and anti-centromere B antibodies) and normal nailfold capillaroscopy. Instead, a high titer of MPO-ANCA was detected. The computerized tomography scan revealed early diffuse interstitial lung disease (ILD). Cases of MPA with pulmonary involvement, such as ILD before the onset of vasculitis or kidney involvement, are known. Therefore, the diagnosis of MPA was formulated considering the symptoms, the clinical examination and the high titer of MPO-ANCA. The particularity of the present case consists in the uncommon onset with atypical skin changes, positivity to MPO-ANCA, absent renal dysfunction and ILD involvement.