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Findings: A high resolution CT (HRCT) of the chest was performed. This shows fine bibasilar and peripheral reticular and nodular densities. Basilar and peripheral honeycombing is present. The posterior segments of the upper lobes show fine ground glass opacities.
Diagnosis: Usual interstitial pneumonitis (UIP)
Discussion: UIP is the most common chronic interstitial pneumonia. It has a variety of names, and is often referred to as idiopathic pulmonary fibrosis (IPF) or in Britain, cryptogenic fibrosing alveolitis(CFA). Pathologically, UIP shows evidence of alveolitis and increased cellularity of the alveolar wall. With progression, fibrosis and honeycombing occur. It is felt the pathologic changes of UIP probably represent an immunologic response to an inhaled or environmental pathogen. Following the initial insult to the endothelial and alveolar epithelial cells, recruitment of alveolar macrophages stimulate neutrophils and fibroblasts, with the progression from an alveolitis to interstitial fibrosis and organization. Proliferation of Type II pneumocytes occur, with deposition of collagen.
UIP occurs in 30-50/100,000 people. It has a slight male predominance, and usually presents in the 5th or 6th decade of life. While it is often idiopathic, approximately 30% have an underlying cause, usually a collagen vascular disorder. A number of other associations have been made, including chronic active hepatitis, primary biliary cirrhosis, ulcerative colitis, and celiac disease.
Patients generally present with dyspnea on exertion and cough. Fine late inspiratory crackles are characteristic on physical exam, and many patients will develop clubbing.
Radiographically, the plain film will show reticulonodular opacities and 25-60% will show decreased volumes. HRCT will show evidence of intralobular and interlobular thickening. Irregular interfaces are seen between the lung and the pulmonary interstitium. Ground glass opacities may be present. While these ground glass opacities were initially felt to be predictive of reversible, active alveolitis, further studies have shown that ground glass opacities can also represent intralobular/alveolar wall fibrosis. Gallium67 activity can be used to assess activity of patients with UIP. CT scans of patients with UIP show a high incidence of lymphadenopathy, and these hyperplastic nodes can grow up to 4 centimeters in size. It is important to screen these people carefully for the development of malignancy, as 5-13% of patients will develop lung cancer.
References:
Armstrong P, Wilson AG, Dee P, Hansell DM. In Imaging of Diseases
of the Chest. Mosby, St. Louis 1995.
Webb WR, Muller NL, Naidich,DP, High Resolution CT of the Lung.
Lippincott-Raven Philadelphia 1996.
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