Presence of heterogeneous, patchy fibrosis with fibroblastic foci is characteristic of usual interstitial pneumonia (a type of idiopathic interstitial pneumonia).Idiopathic interstitial pneumonia (Idiopathic interstitial lung disease)Idiopathic interstitial pneumonias (IIP) comprise a group of diffuse parenchymal lung diseases characterized by various degree of inflammation and fibrosis leading to the destruction of lung architecture. The primary area of damage involves interstitium, but other areas become involved as the disease progresses. Idiopathic denotes an unknown etiology; therefore known causes must be excluded by Careful history and examinations. All IIPs share similar clinical and radiological features and are distinguished primarily by the histopathological pattern on lung biopsy.