Diffuse alveolar hemorrhage (DAH) results from disruption of the alveolar-capillary basement membrane from a variety of primary disease states. These patients often present with hemoptysis, but this symptom can be absent, even in patients with severe DAH. The causes are reflected in the histopathologic patterns:
1) Pulmonary capillaritis is results from neutrophilic infiltration of the lung interstitium which leads to necrosis and loss of capillary structural integrity, then spilling of RBCs into the alveolar space. Major causes of this include:
- Systemic vasculitides: Granulomatosis with polyangitis, microscopic polyangitis, Churg-Straus, Behcet's, cryoglobulinemia, Henoch-Schonolein Purpura, IgA nephropathy
- Rheumatic diseases: Anti-GBM/ Goodpasture's, APLA, SLE, RA, systemic sclerosis, MCTD
- Drugs: Hydralazine, Propylthiouracil, TNF-antagonists, and all-trans retinoic acid (differentiation syndrome)
- Other: Hematopoetic stem cell transplant, lung transplant rejection, isolated pulmonary capillaritis
2) Bland pulmonary hemorrhage results from bleeding in the alveolar spaces without destruction from inflammation. Causes include:
- Increased LV end-diastolic pressure
- Mitral stenosis
- Anticoagulants and antiplatelet medications
- Coagulation disorders
- Connective tissue disease Anti-GBM, SLE can do it, but are usually associated with capillaritis
3) Diffuse alveolar damage is characterized by edema of the alveolar septa and the formation of hyaline membranes in the alveolar spaces, which is the underlying pathophysiology in the development of the Acute Respiratory Distress Syndrome (ARDS). This is typically a result of:
- Drugs and toxins: such as Amiodarone, Amphetamine, Crack, Nitrofurantoin, Penicillamine, Propylthiouracil
Today, we also discussed adding on rapidly progressive glomerulonephritis to DAH and the pulmonary renal syndromes. A nice review from Critical Care (2007) is here.
What are some of the distinguishing characteristics for the 3 ANCA-associated vasculitides? Be the first to comment and answer correctly below and win a Starbucks giftcard!