Bronchoalveolar lavage in adult sickle cell patients with acute chest syndrome: value for diagnostic assessment of fat embolism.

Abstract

Fat embolism of necrotic bone marrow could be a frequent cause of acute chest syndrome (ACS) in sickle cell syndromes (SC), as suggested by postmortem findings. To check this hypothesis in living patients, we evaluated the presence of fatty macrophages recovered by bronchoalveolar lavage (BAL) in ACS. We investigated 20 consecutive cases of ACS by BAL, and identification of alveolar cells containing fat droplets was performed using oil red O (ORO), a specific neutral fat stain. The specificity of the method was determined on control groups, including eight SC patients without acute chest syndrome and 15 non-SC patients. A cut-off of > 5% of alveolar macrophages containing fat droplets was determined from the control groups to assess the diagnosis of fat embolism. In 12 ACS episodes, BAL exhibited > 5% of fatty macrophages, ranging from 10% to 100% (median value 46.5%). In 11 cases, fat embolism was associated with proven (n = 8) or probable (n = 3) bone marrow infraction, which mostly predated ACS. Eight ACS episodes were associated with a low percentage (< or = 5%) of fatty alveolar macrophages and could be related to a cause other than fat embolism in six episodes, such as sepsis, in-situ thrombosis, or rib infarcts generating hypoventilation. This study supports the diagnostic yield of BAL for fat embolism, which can be incriminated in 60% of cases of ACS in this adult population.

Fat embolism

“…As macrophages act as lung scavengers, they might be expected to contain fat in FES. BAL in trauma patients has been proposed as a specific method for diagnosing FES within the first 24 h [22,23]. However, there are difficulties in obtaining satisfactory samples, as shown in one study where only 67 out of 96 samples were adequate for analysis due to low yield of macrophages [24].…”

“…FES is recognised as part of an acute sickle cell crisis [17,23,56]. Acute chest syndrome is the second most common reason for hospital admission and leading cause of death in sickle cell disease.…”

“…Bone marrow necrosis caused by hypoxia and stasis during an acute crisis may release bone marrow fat. In 60% of acute chest syndrome cases, the pulmonary macrophages stain for fat [23] and this is associated with bone marrow infarction as shown by either isotope scanning or magnetic resonance imaging. Biochemical markers such as PLA 2 may increase up to 100 times the usual value found in patients with quiescent sickle cell disease and more than five times greater than a similar control group ill with pneumonia [17].…”

Acute Chest Syndrome in Sickle Cell Disease

“…Initially Streptococcus pneumoniae was considered the most common infectious agent, 9,10 but subsequent research has consistently reported lower rates of pneumococcal disease. 2,7,[11][12][13][14][15] This apparent change may be the result of more rigorous research methodology or therapies developed specifically to prevent pneumococcal disease such as prophylactic penicillin and vaccine administration. 13,16,17 Chlamydia pneumoniae and Mycoplasma pneumoniae are now the most common documented infectious causes of ACS.…”

“…7,13,18,19 Other viral and bacterial organisms that have been linked to ACS include Haemophilus influenzae, Staphylococcus aureus, Klebsiella pneumoniae, adenovirus, influenza viruses, parainfluenza viruses, respiratory syncytial virus, parvovirus B19, and cytomegalovirus. 6,7,[9][10][11][12][13][14][15][18][19][20] …”