 Hello everyone, my topic today is interstitial lung disease and I'm going to talk specifically on the classification and idiopathic pulmonary fibrosis which is the commonest irony. Now there are some 200 diseases which fall under the umbrella of interstitial lung disease. So to simplify it, there are four subgroups. The first group is the one having a known cause or association like drugs, drugs like amyotauron, occupational exposure like pneumoconiosis, silicosis, asbestosis, connective tissue disorder like rheumatoid arthritis, systemic sclerosis. Then comes a group which does not have a known cause and so they are called the idiopathic interstitial pneumonias. The granulomatous group hypersensitivity pneumonitis and sarcoidosis belongs to this group and the rare ILDs like lymphangio myomatosis and pulmonary langerhensil histiocytosis. Idiopathic interstitial pneumonias are again subdivided into four groups by the American Thoracic Society and the European Respiratory Society. This classification was first done in 2002 and then again revised in 2013. The first group is the chronic fibrosin, idiopathic pulmonary fibrosis and non-specific interstitial pneumonia belongs to this group. Then is the smoking related under which comes the squammative interstitial pneumonia and respiratory bronchiolitis associated ILD. Then is the acute subacute group under which is cryptogenic organising pneumonia and acute interstitial pneumonia. Then the rare group lymphocytic interstitial pneumonia and idiopathic pluriparanchymal fibroelastosis belongs to this group. Coming to idiopathic pulmonary fibrosis which we know belongs to the chronic fibrosin type of idiopathic interstitial pneumonia. Now usual interstitial pneumonia is radiological and histopathological pattern associated with idiopathic pulmonary fibrosis. IPF is a progressive chronic fibroletic disease of unknown cause, UIP is 50 to 60 percent of all ILDs and UIP can also be secondary to dust and drug exposure, chronic hypersensitivity pneumonitis, collagen vascular disease, asbestosis and rarely sarcoidosis. The disease presents at more than 50 years of age with gradual onset of symptoms usually more than six months with progressive shortness of breath and dry cough. More common in men, more common in smokers and gradual deterioration is the usual clinical course. Symptoms can be accelerated deterioration, acute exerberation and lung cancer which occurs in 10 to 15 percent of cases. Now histopathology has always been the gold standard for the diagnosis of IPF. It has two characteristic features, one is spatial or geographic heterogeneity which means normal lung interspaced with disease lung and temporarily heterogeneous which means heterogeneous over time which means in the same slide you can see fibrosis in different stages. One is old fibrosis then new fibrosis which is represented by the fibroplastic foci and then comes the normal lung. The normal lung is gradually going to become fibrosis over time. According to the Fleschner society there are three patterns of UIP that are typical, probable and indeterminate and an inconsistent with UIP pattern. In typical UIP there is honey combing with or without bronchic thesis and reticulation in subterial location with basal predominance and there is absence of features inconsistent with UIP pattern. Let us look at these features one by one. So here there is honey combing which are layers of cysts stacked over one another and linear opacities called reticulations. They are in subterial location with basal predominance and here we can see some dilatation of bronchioles due to the pull of the adjacent fibrosis. We need to know what the inconsistent with UIP features are. If the disease distribution is in the middle and upper lungs then it is inconsistent with UIP. If the disease distribution is very bronchovascular again inconsistent with UIP. If there are extensive ground glass opacification more than reticular opacities maybe we are looking at NSIP inconsistent with UIP. Scattered micronodules more than upper lobe maybe we are looking at sarcoidosis we are not looking at UIP. Bilateral multiple cysts away from areas of fibrosis again inconsistent with UIP pattern. Federal air trapping in three or more lobes maybe we are looking at hypersensitivity pneumonitis not UIP. If we are looking at consolidations probably cryptogenic organizing pneumonia not UIP. So if any of these features are present then we are not looking at UIP. Coming to probable UIP the most important thing is there is no honey combing here but we get subplural and basal reticulation with or without ground glass opacities and we get peripheral traction bronchic cases and of course we did not get any findings inconsistent with UIP pattern. Now so far we have been talking about typical and probable UIP where we could have said with confidence that this is IPF but there is yet another pattern which is called indeterminate usual interstitial pneumonia where we get subtle subplural reticulation with or without ground glass opacities something like this where we cannot say for sure that this is usual interstitial pneumonia. This is where the radiologist and clinician gets together and decides that the pathologist is required to do a biopsy for a diagnosis. We need to know the differential diagnosis of UIP to understand whether we are looking at actually idiopathic pulmonary fibrosis or a UIP like pattern as is seen in secondary causes of UIP. So differentiating them is important as it has significant therapeutic and prognostic implications the diseases are connective tissue disorders hypersensitivity pneumonitis drugs like amiodarone and asbestosis. In chronic hypersensitivity pneumonitis we get reticulation and honeycombing just like in IPF but they are more in the upper lobes along with it we also get ground glass opacities and centrilobelanodule and mosaic attenuation like this. In asbestosis we get subplural reticulation and honeycombing but we also look out for subplural lines, paranchymal bands, pleural thickening and calcified or uncalcified pleural plants. In amiodarone lung we get ground glass opacities and septal thickening coexisting with interstitial lung disease but we also get high density nodules and consolidations because of the iodinated chemistry of amiodarone. Coming to connective tissue disorder related ILD they are more associated with NSIP than UIP except rheumatoid arthritis where UIP is more common. Now a recent paper has said that there are three signs which are associated with CTDILD. They are anterior upper lobe sign, exuberant honeycomb sign and the straight edge sign. In anterior upper lobe sign there is honeycombing traction bronchic cases and fibrosis in anterior aspect of the upper lobes with relative sparing of the posterior aspect. The straight edge sign says that the fibrosis is limited to the lung basis with a sharp cut off in the cranial caudal aspect without much extension along the lateral borders. But the sign that is most helpful in my experience is the exuberant honeycomb sign where there is a lot of honeycombing which constitutes almost 70% of the fibrosis in that lung. To summarize a patient of 50 years comes with insidious onset of otherwise unexplained dysplnia on exertion for a duration of more than 3 months. History of medication and environmental exposure is taken. Cereological tests are done to rule out connective tissue disease. HRCT is done which reveals usual interstitial pneumonia. Pulmonary function tests reveal evidence of restriction. We come to the diagnosis of idiopathic pulmonary fibrosis. Remember a timely diagnosis will help the clinician initiate the antifibrotic agents to slow down the progression of the disease and possibly improve survival. Thank you.