From the First Department of Medicine (M.H., K.K., Y.Y., T.M., Y.M.,
T.K., M.S.) and Department of Legal Medicine (M.O.), Shinshu University School
of Medicine, Matsumoto, Japan, and Toyama Citizen Hospital (H.W.), Toyama,
Japan.
Correspondence to Keishi Kubo, MD, First Department of Medicine, Shinshu University School of Medicine, 31-1 Asahi, Matsumoto, 390 Japan.
Methods and ResultsThe frequencies of human leukocyte
antigen (HLA) alleles in 28 male and 2 female subjects with a
history of HAPE were compared with those in 100 healthy volunteers. We
assayed the HLA-A, -B, -C, -DR, and -DQ antigens serologically. The
pulmonary hemodynamics on admission to the
hospital and the ventilatory response to hypoxia and
hypercapnia were retrospectively examined in 10 of the HAPE-susceptible
subjects. HLA-DR6 was positive in 14 (46.7%) of the subjects with HAPE
but only 16.0% of the control subjects (P=.0005), and
HLA-DQ4 was positive in 12 (40.0%) of the subjects with HAPE but only
10.0% of the control subjects (P=.0001). HLA-DR6 or
HLA-DQ4 was positive in 8 (100%) of the subjects with recurrent
HAPE. The pulmonary arterial pressure on admission
of the HLA-DR6positive subjects with HAPE was significantly higher
than that of the HLA-DR6negative subjects with HAPE.
ConclusionsThere were significant associations of HAPE with
HLA-DR6 and HLA-DQ4 and of pulmonary hypertension with HLA-DR6.
An immunogenetic susceptibility, which is associated with HLA class II
alleles located within the major histocompatibility complex, may
underlie the development of HAPE, at least in some of its forms.
In contrast, a striking genetic association has been reported
between certain HLA alleles and susceptibility to some diseases. To
examine whether immunogenetic susceptibility is present in
HAPE-susceptible subjects, we performed HLA typing for A, B, C, DR, and
DQ alleles in subjects with a history of HAPE and compared the
results with those of healthy subjects who were chosen at random
throughout Japan. Moreover, we retrospectively examined the
pulmonary hemodynamics on admission to the
hospital and the ventilatory response to hypoxia and
hypercapnia in some HAPE-susceptible subjects to see whether HLA
alleles might be related to these physiological
parameters.
The subjects with histories of HAPE consisted of 28 males and 2
females, ranging in age from 15 to 75 years with an average age of 30.0
years (Table 1
The control subjects had all been born and resided at altitudes <610 m
in Japan; they had no history of cardiopulmonary diseases.
Measurements
Pulmonary Hemodynamics
Ventilatory Responses
Statistical Analysis
HAPE recurrence was shown in all 8 of the HLA-DR6or
HLA-DQ4positive subjects. Six (42.9%) of the 14 DR6-positive
subjects experienced recurrent episodes versus only 2 (12.5%) of 16
DR6-negative subjects.
Pulmonary Hemodynamics
Ventilatory Responses
Many investigators have pointed out the possibility of a constitutional
susceptibility to HAPE.7 8 Individual
susceptibility may be associated with enhanced pulmonary
vascular reactivity to hypoxia and exercise. We found that
HAPE-susceptible subjects showed a much greater increase in
pulmonary vascular resistance than control subjects, resulting
in a much higher level of pulmonary arterial
pressure, under both acute hypoxia of 15% oxygen and acute
hypobaria of 515 mm Hg.14 Moreover,
HAPE-susceptible subjects exhibited a tendency toward increased
pulmonary vascular resistance even during normoxic light
exercise with a supine bicycle ergometer, therefore showing a greater
increase in pulmonary arterial pressure and greater
decrease in arterial oxygen tension during exercise under
both conditions. Similar observations were described by Hultgren et
al15 and Fasules et al.16
Hultgren et al15 studied HAPE-susceptible subjects both at
sea level and 24 hours after ascent to an altitude of 3100 m.
Although none developed clinical or radiographic evidence
of pulmonary edema, all developed marked pulmonary
hypertension and hypoxemia. Fasules et al16 found that
HAPE-susceptible children had greater pulmonary
arterial pressure than did nonsusceptible children with
acute hypoxia of 16% oxygen.
It has been indicated that pulmonary hypertension plays an
important role in the initiation and development of HAPE, although
pulmonary hypertension itself does not cause pulmonary
edema. The high pulmonary arterial pressure found
in HAPE patients must play a role in the mechanism of the condition,
because the prophylactic administration of
nifedipine was effective in lowering pulmonary
artery pressure and preventing HAPE in susceptible
subjects.17 The inhalation of NO also produced a
decrease in systolic pulmonary artery pressure and
improved arterial oxygenation in
HAPE-susceptible subjects.18 West and
Mathieu-Costello19 20 proposed that HAPE was
caused by damage to the walls of pulmonary capillaries as a
result of very high wall stress associated with increased capillary
transmural pressures that were the result of uneven hypoxic
pulmonary vasoconstriction. In the present study, there was
significantly increased pulmonary arterial pressure
in the HLA-DR6positive HAPE patients breathing room air on admission
to the hospital compared with the HLA-DR6negative patients.
Pulmonary vascular resistance also tended to be increased in
this group. We consider that one of the mechanisms contributing to HAPE
is pulmonary hypertension, which is caused by an increase in
pulmonary vascular resistance resulting from either
microvascular injury or obstruction. The results of the present
study indicate that HLA-DR6 may be related to pulmonary
hypertension.
Recently, it was found that the primary pulmonary
hypertension in HIV infection was associated with HLA-DR6 and
HLA-DR52.21 HIV-associated primary
pulmonary hypertension may reflect a host response to HIV-1
determined by one or more HLA-DR alleles located within the major
histocompatibility complex. Moreover, the presence of HLA-DR6 and
HLA-DR52 was associated with significantly increased risk of a fatal
disease outcome with pulmonary hypertension in
scleroderma.22 The expression of
pulmonary hypertension appears to require an environmental
trigger or additional genes. Multiple heterogeneous
immunologic events also play a role in the development of
pulmonary hypertension.23 The possible
routes include vasculitis with immune complex deposition, the induction
of activation molecules such as HLA class II on
endothelial cells with inflammatory infiltrates, and
release of cytokines and mediators (T-cellmediated vascular
injury) and initiation of noninflammatory vasculopathy via procoagulant
activity (recurrent thromboembolism, thrombosis in situ, or both). The
release of inflammatory cytokines and vasoconstricting
mediators could follow any of these pathways.23
We24 recently reported that endothelin-1 is a
vasoconstrictor that contributed to the pulmonary hypertension
in HAPE. We also showed that there were significant increases in
the levels of total cells (especially macrophages and
neutrophils), total protein, albumin, IL-1, IL-6, IL-8, and
tumor necrosis factor-
The pathogenesis of HAPE is multifactorial. Various mechanisms take
part in the initiation of the condition and its progression. We
postulate that both immunologic events and inflammatory processes are
important in the development of HAPE, which occurs at moderate
altitudes and affects young people recurrently. The clinical evidence
linking HAPE to inflammatory processes is that the onset of HAPE
occurred 48 to 96 hours from the beginning of
ascent5 and that acute hypoxia did not
cause pulmonary edema in HAPE-susceptible subjects in previous
studies.14 15 16 A period of 48 to 96 hours may be
sufficient for the inflammatory process to progress to the point of the
initiation of HAPE. Moreover, dexamethasone, an effective
immunosuppressive agent, has been successfully used to prevent and
treat acute mountain sickness.26
It is clear, at least, that HAPE occurs in relationship to both
environmental and individual factors. The environmental factors are
unique to high altitude and include hypoxia, hypobaria, and low
temperatures. The individual factors include susceptibility to
hypoxia, hypobaria, or exercise, each of which enhances
pulmonary hypertension, and associated conditions experienced
during a period at high altitude, such as upper respiratory infection.
One of the possible explanations for the pathogenesis of HAPE is that
an initial event, such as upper respiratory infection, may induce a
host response to the environmental factors associated with HLA class II
alleles, then an inflammatory process may occur and lead to
pulmonary hypertension resulting in HAPE. Actually, Fasules et
al16 suggested that upper respiratory infections
may play a role in the pathogenesis of HAPE.
In summary, increased frequencies of HLA-DR6 and HLA-DQ4 in subjects
with HAPE were demonstrated. All eight subjects with recurrent episodes
of HAPE had either HLA-DR6 or HLA-DQ4. HLA-DR6positive patients with
HAPE showed a significant increase in pulmonary
arterial pressure on admission. These findings suggest that
susceptibility to HAPE is associated with major histocompatibility
complex alleles, notably with HLA-DR6 or HLA-DQ4, either alone or
in combination. We conclude that HLA class II alleles located
within the major histocompatibility complex may contribute to the
individual factors, ie, constitutional susceptibility, in the
development of some types of HAPE.
Received August 18, 1997;
revision received November 3, 1997;
accepted December 1, 1997.
© 1998 American Heart Association, Inc.
Clinical Investigation and Reports
Association of High-Altitude Pulmonary Edema With the Major Histocompatibility Complex
![]()
Abstract
Top
Abstract
Introduction
Methods
Results
Discussion
References
BackgroundA constitutional
susceptibility has been suggested in the development of high-altitude
pulmonary edema (HAPE) because HAPE generally affects healthy
young people, some of whom suffer recurrent episodes. We examined
whether immunogenetic susceptibility is present in
HAPE-susceptible subjects.
Key Words: edema genetics hemodynamics hypertension, pulmonary ventilation
![]()
Introduction
Top
Abstract
Introduction
Methods
Results
Discussion
References
Some mountain
climbers who have no past history of any cardiopulmonary
problems experience HAPE, a severe form of acute mountain sickness,
after rapid ascent to altitudes in excess of 2700 m above sea
level.1 2 3 4 This form of noncardiogenic
pulmonary edema is rare and is sometimes complicated with
cerebral edema or retinal hemorrhage. A few cases of HAPE are
reported every year in Japan, and some of these patients are
transported to our institution, Shinshu University Hospital (610 m
above sea level), or Toyama Citizen Hospital (10 m above sea level)
from the "Japan Alps" of the central area of
Japan.5 HAPE generally affects healthy young
people, some of whom suffer recurrent
episodes.6 7 It often occurs at moderate
altitudes in Japan. For these reasons, it has been speculated that a
constitutional susceptibility underlies the development of this
disease. We observed 51 cases of HAPE from November 1971 to September
1996, and 10 (19.6%) were recurrent episodes. These findings appear to
support the previous observation that individuals who have developed
HAPE are more likely to experience future episodes than the general
population.
![]()
Methods
Top
Abstract
Introduction
Methods
Results
Discussion
References
Subjects
We examined 30 subjects with histories of HAPE and 100 control
subjects. All subjects were healthy adult natives of Japan, and none
were taking any medication. All subjects gave informed
consent.
). They had all been born
and resided at low altitude (<610 m) and had experienced at least one
episode of HAPE requiring hospitalization while climbing in the Japan
Alps. Eight (26.7%) of them had had recurrent episodes. The altitude
at the onset of HAPE ranged from 2857 to 3190 m above sea level.
We diagnosed HAPE on the basis of the following
criteria8 : onset at high altitude of the typical
symptoms, including cough and dyspnea at rest; absence of
infection; presence of pulmonary rales and cyanosis;
disappearance of symptoms and signs within 3 days of the start of
treatment with bed rest and supplemental oxygen; and chest
roentgenographic infiltrates consistent with pulmonary
edema. All subjects with HAPE met all criteria at the onset of the
disorder and recovered promptly and well with hospitalization. They
were all in good health at the time of the present study.
View this table:
[in a new window]
Table 1. Age, Sex, Symptoms, and Blood Gas Values During HAPE
in Each of the 30 Subjects With HAPE
HLA Typing
Venous blood samples were obtained from the patients and control
subjects. Lymphocytes were isolated from peripheral blood
by use of a density gradient centrifugation
technique,9 and B cells were separated with
Lympho-Kwik reagent (One Lambda). The mononuclear cells were subjected
to HLA-A, -B, and -C typing with a standard microcytotoxicity
test,10 whereas HLA-DR and HLA-DQ typing was
performed on the B cells by use of a similar technique but with
prolonged incubation times.11
Of the 30 subjects with HAPE, 10 (9 male subjects and 1 female
subject) had undergone pulmonary hemodynamic
studies. Right cardiac catheterization during room air
breathing was performed within 6 hours after admission to Shinshu
University Hospital. A thermodilution Swan-Ganz catheter was introduced
percutaneously into the pulmonary artery via
the right internal jugular vein. The pulmonary
arterial pressure and pulmonary
arterial wedge pressure were measured on a transducer
system with the use of a calibrated pressure transducer (Statham P50),
and cardiac output was measured by the thermodilution method with the
use of a cardiac computer (Edwards 9520A). We calculated
pulmonary vascular resistance by subtracting pulmonary
arterial wedge pressure from pulmonary
arterial pressure and dividing by the cardiac output.
After complete recovery, ventilatory responses were also
measured in the same 10 subjects with HAPE with the use of a
rebreathing system. Ventilatory responses were assessed by use of the
progressive isocapnic HVR described by Weil et
al12 and the HCVR described by
Read.13 We evaluated the HVR using the slope of
linear regression between VE and
SaO2. This slope is termed
VE/
SaO2. A high
slope value indicates a brisk ventilatory response to hypoxia.
HCVR was analyzed from the equation VE=S(PETCO2-B),
where S is the slope of the line derived from plotting
VE versus end-tidal CO2 partial
pressure (PETCO2) and
B is the extrapolated intercept of the
PETCO2
axis.13 Values were measured after an
equilibration period. A high slope value also indicates a brisk
ventilatory response to hypercapnia. All studies were conducted at
Shinshu University Hospital.
HLA data were analyzed by the standard statistical
procedure of
2 contingency table
analysis and Fisher's exact test. The OR was provided by the
cross-product ratio (incidence ratio) of the entries in the 2x2
table (ie, ad/bc). Data for pulmonary
hemodynamics and ventilatory responses are expressed as
mean±SEM. Comparison of data between the subgroups of HAPE-susceptible
subjects was made by use of the Student's t test. A value
of P<.05 was considered significant.
![]()
Results
Top
Abstract
Introduction
Methods
Results
Discussion
References
HLA Typing
The frequencies for the HLA class II alleles in the subjects
with HAPE and the control subjects are shown in Table 2
. HLA-DR6 and -DQ4 were significantly
more frequent in the subjects with HAPE than in the control subjects.
DR6 was positive in 14 (46.7%) of the subjects with HAPE but in only
16.0% of the control subjects (P=.0005, OR=4.6). DQ4 was
positive in 12 (40.0%) of the subjects with HAPE but only 10.0% of
the control subjects (P=.0001, OR=6.0). In 4 of the subjects
with HAPE, both DR6 and DQ4 were positive. There was also a significant
difference for HLA-B44 (26.7% of HAPE subjects versus 11.0% of the
control subjects; P=.042, OR=2.9). In the HAPE subjects, the
B44 allele was frequently expressed; however, the increase of the
B44 antigen frequency was consistent with the linkage
disequilibrium of B44 and DR6 in Japanese individuals. For other HLA
types, there was no significant difference in frequency between the two
groups.
View this table:
[in a new window]
Table 2. Frequency of HLA-DR and -DQ Antigens in Subjects
With HAPE and Control Subjects
Pulmonary hemodynamics on admission were
examined separately in the DR6-positive (n=5) and DR6-negative (n=5)
subjects. In both subgroups, pulmonary
hemodynamic data (Table 3
) demonstrated normal pulmonary
arterial wedge pressure, normal cardiac output, and
increased pulmonary vascular resistance. The pulmonary
arterial pressure, however, was significantly increased in
the DR6-positive subgroup (P<.05).
View this table:
[in a new window]
Table 3. Pulmonary Hemodynamics and
Ventilatory Responses in Subjects With HAPE
Ventilatory responses were also examined separately in the
two subgroups (n=5 each). There were no significant differences between
the subgroups in either HVR or HCVR (Table 3
).
![]()
Discussion
Top
Abstract
Introduction
Methods
Results
Discussion
References
The most noteworthy immunogenetic findings in the 30 subjects with
HAPE were the increased frequencies of HLA-DR6 and HLA-DQ4 compared
with those in the control subjects. HAPE occurred recurrently in all 8
subjects who had either HLA-DR6 or HLA-DQ4 and in 6 of the 14
DR6-positive subjects. Furthermore, the HLA-DR6positive patients with
HAPE showed a significant increase in pulmonary
arterial pressure on admission compared with the
HLA-DR6negative patients with HAPE.
in bronchoalveolar lavage fluid in patients
with HAPE compared with the values after recovery, suggesting that an
inflammatory process may occur in HAPE.25 It is
believed that an inflammatory process resulting from immunologic
events, triggered and enhanced by environmental factors, may lead to
pulmonary hypertension resulting in HAPE.
![]()
Selected Abbreviations and Acronyms
HAPE
=
high-altitude pulmonary edema
HCVR
=
hyperoxic hypercapnic ventilatory response
HLA
=
human leukocyte antigen
HVR
=
hypoxic ventilatory response
IL
=
interleukin
OR
=
odds ratio
SaO2
=
arterial O2 saturation
VE
=
minute ventilation
![]()
Acknowledgments
The authors greatly appreciate the kind suggestions of Robert B.
Schoene, MD, Professor of Medicine, Harborview Medical Center, Seattle,
Wash, for our paper. They thank Drs R. Ge, D. Yunden, K. Fujimoto, T.
Honda, T. Koizumi, S. Yoshikawa, S. Horie, M. Hayasaka, T. Hayano, K.
Okada, T. Hachiya, H. Nomura, E. Sato, and S. Yamaguchi for their
generous support of this study. They are also grateful to SRL Co
(Tokyo, Japan) for technical assistance in the serological assay
of HLA.
![]()
References
Top
Abstract
Introduction
Methods
Results
Discussion
References
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