Life-threatening acute pneumonitis in mixed connective tissue disease: a case report and literature review.

Mixed connective tissue disease (MCTD) is a rare connective tissue disease frequently involving the lungs. The main characteristic is a systemic sclerosis-like picture of slowly progressing interstitial lung disease consistent with lung fibrosis, while pulmonary arterial hypertension is rare. Herein, we present a case of a newly diagnosed MCTD patient developing life-threatening acute pneumonitis similar to lupus pneumonitis. Previous literature on this exceptionally rare complication of MCTD is reviewed and differential diagnosis and management discussed.