BG11 Neutrophilic dermatosis: an unexpected pathway to diagnosing rheumatoid arthritis in a 73-year-old woman

Abstract A 73-year-old woman with a history of an embolic stroke, hypertension and hypercholesterolaemia presented with a 4-month history of a persistent rash affecting her legs. She had not commenced any new medications. On examination, there was a symmetrical, erythematous, papular rash over the lower limbs. This responded well to a course of oral prednisolone but relapsed quickly upon tapering. A diagnostic punch biopsy was performed. Histology showed nonspecific changes, including hyperkeratosis and a perivascular, chronic lymphocytic infiltrate. The patient reported haemorrhagic bullae on the feet, which had resolved by the time of review. A subsequent incisional biopsy was significant for florid dermal inflammation, comprising neutrophils, eosinophils, lymphocytes and histiocytes with associated leucocytoclasis. A diagnosis of neutrophilic dermatosis was made. Treatment with oral prednisolone, 30 mg daily for 1 week, with a slow taper and dapsone 100 mg once daily was commenced. Computed tomography of the thorax, abdomen and pelvis was undertaken to exclude a paraneoplastic process and was normal. After 2 months, the patient developed a new anaemia, with haemoglobin 10 g dL−1 (normal range 11.7–15.9). Dapsone was continued with close blood monitoring; however, the patient was subsequently admitted to hospital with a cough, shortness of breath and profound fatigue. She was found to be in type 1 respiratory failure. Serological investigations showed a white cell count 15.4 × 109 cells L−1 (normal range 4.4–11.3 × 109), with a neutrophilia of 12.4 × 109 cells L−1 (normal range 1.4–6.6 × 109) and C-reactive protein 81 mg L−1 (normal range 0–10). Flu and COVID-19 were not detected. Computed tomography of the thorax showed mild, early pulmonary fibrotic changes, which were thought to be secondary to dapsone. This was discontinued immediately. Upon cessation, the rash flared significantly with new plantar fissuring and extension to the abdomen. Oral prednisolone was reinitiated. A bronchoscopy was performed. Respiratory culture was negative for acid-fast bacilli. Fungal culture is ongoing; however, no fungal elements were seen on bronchoalveolar lavage. The patient subsequently attended a dermatology departmental meeting, where the possibility of rheumatoid arthritis was raised, given the presence of firm, subcutaneous nodules that had developed over the elbows, consistent with rheumatoid nodules. Rheumatoid factor was elevated at 134 IU mL−1 (normal range 0–10). We hypothesize that the early signs of lung fibrosis are potentially attributable to her hitherto undiagnosed rheumatoid arthritis. A rheumatology opinion has been sought. This case highlights the challenges in managing neutrophilic dermatosis in older patients, particularly when complicated by comorbidities. The patient’s evolving clinical picture, including the possibility of rheumatoid arthritis contributing to both her skin and pulmonary manifestations, underscores the importance of a multidisciplinary approach in diagnosing and managing complex dermatological cases in older patients.