Hematological disorders. Azoulay and coworkers (111) report
20 patients with respiratory impairment as the presenting
manifestation of undiagnosed acute monocytic leukemia. All of
the patients had myeloid leukemia of the AML5 subtype. The
median leukocyte count was 98,250 per mm3 and all but one
patient had circulating monocytic cells. Patients presented with
a respiratory rate of 33 breaths per minute, Po2 (room air) of
45 mm Hg, and variable changes on chest X-ray. Alveolar hemorrhage
was the main finding on bronchoalveolar lavage. Respiratory
function deteriorated in every patient with a few hours of
starting chemotherapy. Ten of 15 patients requiring mechanical
ventilation died. The authors conclude that acute pulmonary
infiltration resulting in respiratory failure can be the presenting
manifestation of acute monocytic leukemia, and that patients
require intensive management in anticipation of deterioration
after commencing chemotherapy.
More than 40% of patients who develop acute chest syndrome
secondary to sickle cell disease have fat droplets in their alveolar
macrophages, which are suggestive of pulmonary fat embolism.
To determine the reliability of induced sputum for diagnosing
fat embolism, Lechapt and coworkers (112) did two studies. In
20 patients with acute chest syndrome, the number of Oil Red
O–stained macrophages in induced sputum was correlated with
the number in bronchoalveolar lavage fluid (Spearman’s coeffi-
cient, 0.66). In a second group of 60 patients with episodes of
acute chest syndrome, sputum induction was successful in 47
patients. A diagnosis of pulmonary fat embolism (based on 5%
of macrophages staining with Oil Red O) was made in 29 of the
47 patients with acute chest syndrome (61.7%) and none of 9
patients who did not have acute chest syndrome. Compared
with patients who had acute chest syndrome but did not have
pulmonary fat embolism, the patients with fat embolism were
more likely to have additional extrathoracic pain (76 versus
50%), neurologic symptoms (7 versus 0%), abnormal transaminases
(28 versus 17%), and a lower differential platelet count
(49 versus 85). The authors conclude that staining of induced
sputum is a useful test for diagnosing pulmonary fat embolism
in patients who have acute chest syndrome secondary to sickle
cell disease.