MORPHOLOGYRegardlessoftheiretiology,allformsofpulmonaryhypertensionareassociatedwithmedial hypertrophy of the pulmonary muscular and elastic arteries, pulmonary arterial atherosclerosis, and right ventricular hypertrophy. Thepresenceoforganizingorrecanalizedthrombifavorsrecurrentpulmonaryemboliasthecause,andthecoexistenceofdiffusepulmonaryfibrosis,orsevereemphysemaandchronicbronchitis,pointstochronichypoxiaastheinitiatingevent.Thevesselchangescaninvolvetheentirearterialtree,fromthemainpulmonaryarteriesdowntothearterioles(
Fig.13.26 ).Inseverecases,atheromatousdepositsforminthepulmonaryarteryanditsmajorbranches.Thearteriolesandsmallarteriesaremostprominentlyaffectedbymedialhypertrophyandintimalfibrosis,sometimesnarrowingthelumenstopinpointchannels.Anuncommonbutcharacteristicpathologicchangeistheplexiform lesion, socalledbecauseatuftofcapillaryformationsispresent,producinganetwork,orweb,thatspansthelumensofdilatedthin-walled,smallarteriesandmayextendoutsidethevessel.
Pulmonary hypertension produces symptoms when the disease is advanced. Idiopathic pulmonary hypertension is most common in women 20 to 40 years of age and occurs occasionally in young children. The presenting features are usually dyspnea and fatigue, but some patients have anginal chest pain. Over time, respiratory distress, cyanosis, and right ventricular hypertrophy appear, and death from decompensated cor pulmonale, often with superimposed thromboembolism and pneumonia, ensues within 2 to 5 years in 80% of patients.
Fig. 13.26 Vascularchangesinpulmonaryhypertension.(A)Atheromafor-mation,achangeusuallylimitedtolargepulmonaryarteries.(B)Markedmedialhypertrophy.(C)Plexiformlesioncharacteristicofadvancedpulmo-naryhypertensionseeninsmallarteries.
Treatment choices depend on the underlying cause. For those with secondary disease, therapy is directed at the trigger (e.g., thromboembolic disease or hypoxemia). A variety of vasodilators have been used with varying success in those with group 1 disease or refractory disease belonging to other groups. Lung transplantation is the definitive treatment for selected patients.
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Pulmonary hemorrhage is a dramatic complication of some interstitial lung disorders. Among these so-called “pulmonary hemorrhage syndromes” are (1) Goodpasture syndrome, (2) idiopathic pulmonary hemosiderosis, and (3) granulomatosis with polyangiitis.
Goodpasture syndrome is an uncommon autoimmune disease in which lung and kidney injury are caused by circulating autoantibodies against certain domains of type IV collagen that are intrinsic to the basement membranes of renal glomeruli and pulmonary alveoli. The antibodies trigger destruction and inflammation of the basement membranes in pulmonary alveoli and renal glomeruli, giving rise to necrotizing hemorrhagic interstitial pneumonitis and rapidly progressive glomerulonephritis.
MORPHOLOGYThelungsareheavyandhaveareasofred-brownconsolidationduetodiffuse alveolar hemorrhage. Microscopicexaminationshowsfocalnecrosisofalveolarwallsassociatedwithintra-alveolarhemorrhage,fibrousthickeningofsepta,andhypertrophictypeIIpneumocytes.Thereisabundanthemosiderin duetoearlierepisodesofhemorrhage(