necrobiotic lung nodules

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Necrobiotic pulmonary nodules are sterile cavitating lung nodules associated with rheumatoid arthritis and inflammatory bowel disease (more often with ulcerative colitis than Crohn disease).

Epidemiology

They are more common in men .

Associations

Caplan syndrome

Clinical presentation

Usually, they are asymptomatic, with symptoms tending to occur when there is rupture of those nodules (e.g. superimposed infection or bronchopleural fistula formation).

Pathology

Histologically, necrobiotic nodules consist of a core of fibrinoid necrosis and sterile aggregate of numerous epithelioid histiocytes arranged in indistinct nodules with an infiltrate of lymphocytes, plasma cells, and multinucleated giant cells. Features are those of a granuloma .

Methotrexate has been implicated to an increase incidence of necrobiotic nodules due to activation of adenosine A1 receptors and consequent cellular fusion into multinucleated giant cells .

Radiographic features

can be single or multiple nodules
predominance in a subpleural distribution
often cavitate

Treatment and prognosis

Although typically regress with treatment of the background disease, they may regress spontaneously. Treatment of rheumatoid arthritis with methotrexate can lead to a paradoxical enlargement of the nodules .

Complications

When a rupture of a necrobiotic nodule occurs, complications might include :

pleural effusion
superimposed infection
bronchopleural fistula

Differential diagnosis

atypical pulmonary infection