A 22 year old presents to his physician with hemoptysis and hematuria with basement membrane antibodies. Most likely diagnosis is -

Ans. is 'b' i.e., Good pasture's syndrome o Good pasture's syndrome is an autoimmune disease characterized by formation of anti GBM antibodies that attack both pulmonary capillaries and the glomerulus (GBM).Good pasture's syndrome|Antibodies against non collagenous domain (NCL) of a3 chain of collagen type IV(Found in Glomerular basement membrane & pulmonary capillaries)|Damage to basement membrane of glomeruli and pulmonary' capillaryAntibodies aganist glomerularAntibodies against pulmonary capillariesBasement membrane (GBM) Glomerulonephritis /Renal diseasePulmonary manifestationso Features of acute glomerulonephritis (RPGN)o Hemoptysis (frank)* HematuriaHemoptysis is largely confined to smokers* Proteinuriao Dyspnea* FdemaX-ray finding* Rapidly progressive renal failureo Diffuse bilateral pulmonary infiltrateso Pathology o Diffuse crescenteric glomerulonephritis Linear IgG staining along basement membrane on immunofluorescence Laboratory features in Good pasture's sy ndromeo Circulating anti GBM antibodies (IgG) : Positiveo A MCA antibodies : Typically negative (May be present in upto 30%)o ANA antibodies : Usually normalo C3 les'els : Usually normal