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Alveolar hemorrhage (AH), diffuse AH (DAH)

(Fr: hémorragie alvéolaire pure, isolée, sans auto-Ac). Diffuse bland alveolar hemorrhage (DAH). Can be severe or fatal (PMID 26236607). When unassociated with pulmonary vasculitis or capillaritis, the condition is named bland diffuse alveolar hemorrhage (DAH). Caution: hemosiderin-laden BAL macrophages can be found in DAD (PMID 19129275). Laboratory clues to this condition include ANA, ANCA, platelets and coagulation studies (INR, and full blood count). DAH may unravel thrombocytopenia (that may be drug-induced), coaculopathy, ANA- or ANCA- and, less often, anti-GBM-(drug)-related disease. Pulmonary capillaritis is more often suspected than proved, as the lung biopsy is generally avoided if typical gross BAL features for AH are present. ANCA of MPO-, HNE- or, less often, -PR3 with multispecificity and high titers suggest the drug etiology. Drug-induced DAH can mimic primary ANCA-related micropolyangiitis or 'Wegener's'. See PMID 19592204, 20442117, 21606695, 21674416. A search for underlying pulmonary condition at the origin of hemorrhage (e.g. lung cancer, bronchiectasis) is indicated. See also under IIIb, VId, Xs, Xz, XVIIv. 2018 review @PMID 30404115