Pulmonary necrobiotic nodules (PNN) are rare and are usually associated with rheumatoid arthritis (RA).12 PNN in the absence of arthritis is an even rarer entity and may precede the evidence of RA by as many as 11 years.3 Several cases are described in the literature as idiopathic.3
A 50 year-old asymptomatic white male was found to have right upper lobe opacity on a chest x-ray. He had a 100-pack year smoking history and a 22-year history of occupational exposure to flue dust from a steel blast furnace in a motor company. Physical examination revealed severe finger and toe clubbing. There was no evidence of joint tenderness, effusion, or synovitis. Laboratory studies including ANA and rheumatoid factor were unremarkable. Computed tomography of the chest showed a 2.8 cm nodule in the right upper lobe in addition to extensive emphysema and numerous subpleural bullae. Right upper lobectomy was performed and the histopathology showed necrobiotic granulomatous inflamation and patchy fibrosis.There were ferruginous bodies on iron stain and numerous iron-containing macrophages. His clubbing remarkably improved within months of retirement from his work.DISCUSSION: Our patient was exposed to blast furnace flue dust containing 20-30% iron oxide for a period of 22 years. The histopathological findings of ferruginous bodies and iron-containing macrophages suggest that the necrobiotic nodule is related to the patient’s exposure, and we have excluded the most common cause of PNN, rhematoid arthritis. The rapid improvement of the clubbing following the patient’s early retirement also supports the relationship between the disease process and the inhalational exposure.
In our patient, we have shown evidence to support the relationship between the exposure to blast furnace flue dust and PNN, which has not been previously described in the literature. Futher case studies are needed to support our findings.
S.T. Morcos, None.