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Response to rituximab of pseudotumoral digital nodules in a patient with granulomatosis with polyangiitis with alpha‐1 antitrypsin deficiency: A case report

Dear Editor, Dermatologic manifestations of alpha-1-antitrypsin (AAT) deficiency (AAD) are rare. AAD has been found associated with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). Nonetheless, we lack an accurate clinical and pathological description of AAV in the setting of AAD. We describe a case of myeloperoxydase (MPO)positive granulomatosis with polyangiitis (GPA) associated with AAD, showing pseudotumoral digital nodules and necrotizing extravascular granulomas on skin biopsy. Of note, after failure of systemic prednisone and methotrexate, rituximab was added, with striking improvement of cutaneous lesions. A 51-year-old man presented bilateral cutaneous nodules on metacarpophalangeal and interphalangeal joints (Figure 1) and had arthritis of both wrists and hands for several months. Differential diagnoses initially considered were erythema elevatum diutinum, sarcoidosis, multicentric reticulohistiocytosis, granulomatous vasculitis, and rheumatoid nodules. The patient had a history of multiple otitis media episodes, explored with tympanic biopsy, which revealed an inflammatory granuloma. Sinus computed tomography (CT) scan revealed abnormalities of a maxillary sinus. Laboratory findings showed moderately altered liver enzyme levels and positivity for MPO-ANCA. Skin biopsies revealed extravascular necrotizing granulomas with a dense dermohypodermal histiocytic infiltrate, a center of mild arcuate and splaying areas of basophilic necrosis and surrounded by histiocytes without significant palisade, which ruled out palisading neutrophilic granulomatous dermatitis. No vasculitis was seen (Figure 2). Moreover, with gradually worsening dyspnea on exertion, respiratory function tests showed an obstructive pattern. CT scan of the chest revealed bilateral ground-glass opacities and signs of emphysema. Because the patient was not a smoker, serum AAT level was measured and found low. A genetic test confirmed the diagnosis of AAD (Pi*SZ phenotype). GPA with sinus, ears, articular, and cutaneous involvement associated with AAD was diagnosed by using the European Medicines Agency algorithm. Our patient received oral prednisone at 30 mg/day and methotrexate 20 mg/week for 18 months. Owing to persisting arthritis and cutaneous lesions, rituximab, 375 mg/m was added to methotrexate at weeks 0, 1, 2, and 3, which led to regression of all symptoms, and