Idiopathic Pulmonary Fibrosis
Describe the salient epidemiologic, clinical, physiologic, and radiographic features of idiopathic pulmonary fibrosis, nonspecific interstitial pneumonia/fibrosis, and sarcoidosis.
Discuss the salient features seen on high-resolution CT scans and their impact on prognosis.
Review the characteristic histopathologic features of each of these disorders and the role of transbronchial or surgical (open or thoracoscopic) lung biopsies.
Discuss the clinical role (if any) of ancillary studies such as radionuclide scanning or BAL to stage or follow up these disorders.
Review therapeutic strategies.
Idiopathic pulmonary fibrosis (IPF) is a specific form of chronic interstitial pneumonia associated with the histologic. Clinical features of IPF include progressive cough, dyspnea, restrictive ventilatory defect, and progressive fibrosis and destruction of the lung parenchyma. IPF is rare (prevalence 13–42 cases/100,000), and primarily affects older adults (age >50 years). The diagnosis of IPF often requires surgical lung biopsy (SLB), but the diagnosis can be affirmed with confidence in some patients provided CT imaging and clinical features are consistent. The clinical course is variable, but inexorable progression (typically over months to years) is typical. Mean survival from the onset of symptoms approximates 3 to 5 years. Medical treatment is largely ineffective. Lung transplantation is the best therapeutic option. Another rare interstitial lung disease, termed nonspecific interstitial pneumonia (NSIP), shares clinical features in common with IPF, but has distinct differences in histologic findings and prognosis. SLB is necessary to substantiate the diagnosis of NSIP. Corticosteroids or immunosuppressive agents may be efficacious in NSIP, but are ineffective in IPF. The relationship between NSIP and usual interstitial pneumonia remains uncertain. Sarcoidosis is a granulomatous disease of uncertain etiology that involves the lungs or intrathoracic lymph nodes in >90% of patients. However, virtually any organ can be involved. Sarcoidosis is worldwide in distribution, but the prevalence varies according to racial and geographic factors. More than two-thirds of patients present between the ages of 20 and 40 years. The natural history of sarcoidosis is usually favorable (spontaneous remissions occur in >50% of cases), but the disease is chronic and progressive in 15% to 30% of patients, resulting in permanent damage and fibrosis of affected organs. Fatality rates range from 0.5% to 4%. Corticosteroids are the mainstay of therapy, and may produce dramatic remissions in patients with severe or progressive sarcoidosis. Immunosuppressive agents may have a role in patients failing or experiencing adverse effects from corticosteroids. Lung transplantation is a therapeutic option for patients with severe pulmonary sarcoidosis refractory to medical therapy.