Clinical features:
(1) The patient presents as idiopathic pulmonary arterial hypertension (PAH) with elevated mean pulmonary artery pressure (> 25 mm Hg) but normal pulmonary capillary wedge pressure (PCWP).
(2) Some patients may give a family history of PVOD, with mutations in the bone morphogenetic protein receptor II (BMPR2)
(3) Patients may show digital clubbing, Raynaud's phenomenon, and syncope or near syncope.
(4) The patient often shows a poor response to vasodilator therapy used in PAH. Vasodilator therapy may trigger acute pulmonary edema which can be life-threatening.
The diagnosis may be suspected based on findings seen on a high resolution CT scan (see previous section.
Laboratory and pulmonary function test (PFT) findings:
(1) low PaO2 at rest
(2) low DLco with a ratio of DLco to alveolar volume < 55%
(3) low SpO2 (pulse arterial oxygen saturation) during a 6-minute walk test
(4) Patients may show evidence of occult alveolar hemorrhage on BAL (hemosiderin laden macrophages).
The gold standard for the diagnosis is a lung biopsy that includes pulmonary veins and venules. The key pathologic findings is initimal thickening causing diffuse, extensive obstruction of pulmonary veins and venules (postcapillary blood vessels). The thickening may involve muscularization, fibrosis and/or cellular proliferation. Pulmonary capillaries may show dilatation and/or proliferation. Unfortunately many patients are too sick to undergo a lung biopsy.
Overall the prognosis is poor unless a lung transplant can be performed.
