IDIOPATHIC PULMONARY HEMOSIDEROSIS
Idiopathic pulmonary hemosiderosis (IPH) is a disease of unknown origin, usually occurring in children, equally in both genders. Repeated episodes of pulmonary hemorrhage with resultant blood-loss anemia and eventual respiratory failure characterize the illness. In children, this disorder is associated with celiac disease and elevated IgA levels. Environmental exposure to molds, particularly Stachybotrys chartarum, has been suggested as a causative factor in infants with IPH, but the relationship remains unproven.
Bland pulmonary hemorrhages without immune complexes
are typical histologic findings. A structural defect in the alveolar capillaries
may predispose individuals to the condition. Neutrophilic infiltration (i.e.,
alveolar capillaritis or vasculitis) is not found. Repeated hemorrhages result
in hemosiderin-laden alveolar macrophages and the deposition of free iron in
pulmonary tissue; the latter may result in the development of lung fibrosis.
Obliteration of alveolar capillaries may result in pulmonary hypertension.
Hemosiderin-impregnated nodules are scattered in the parenchyma, along the
lymphatics, and in the draining hilar lymph nodes. The role of immunologic
injury in patients with IPH remains unclear.
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The onset of IPH may be insidious or with an explosive
episode of hemoptysis. In some patients, anemia, constitutional symptoms,
cough, and radiographic changes precede frank hemoptysis. During acute bleeding
episodes, crackles, wheezes, and rhonchi with dullness to percussion are noted
over the involved lung areas. Later, dyspnea, tachypnea, hepatosplenomegaly,
and clubbing of the fingers may be observed.
Routine laboratory data are remarkable only in the
presence of marked iron deficiency. There is no evidence of coagulopathy,
thrombocytopenia, hepatic dysfunction, or glomerulonephritis.
Physiologic abnormalities in IPH vary depending on the
freshness of the hemorrhage, degree of fibrosis, and severity of vascular
involvement. With acute hemorrhage, the vital capacity, flow rates, and arterial
Po2 may be diminished; however, the DLCO (diffusing capacity for carbon
monoxide) may be inappropriately high. As fibrosis ensues, a restrictive pattern
with reduced DLCO emerges. Irreversible pulmonary hypertension and right
ventricular failure are hallmarks of the end stage of the disease.
During acute hemorrhagic episodes, the chest radiograph exhibits patchy or diffuse alveoli-filling shadows. These opacities may
clear rapidly, only to appear in the same or other locations with subsequent
bouts of hemorrhage. Air bronchograms are frequently obtained. High-resolution
computed tomography (HRCT) scans show diffuse ground-glass or airspacefilling
opacities most prominent in the middle and lower lung fields. With repeated
episodes, a reticular interstitial pattern persists in the areas of prior
hemorrhage. The hilar lymph nodes may become enlarged. In the later stages,
right ventricular hypertrophy and enlarged pulmonary arteries are common.
Perfusion lung scanning with technetium-99m (99mTc) labeled albumin particles may show
foci of high radioactivity in the lungs where radioactively tagged material has
extravasated into the alveoli. In addition, active intrapulmonary bleeding can be
visualized by pulmonary radioscintigraphy, in which autologous erythrocytes
labeled with 51Cr or 99mTc are injected intravenously with subsequent recording
of the radioactivity over the lungs.
IPH is a diagnosis of exclusion that is suggested by a
history of recurrent episodes of hemoptysis, presence of an iron deficiency
anemia, and typical radiographic abnormalities in a child with normal renal
function. Sequential bronchoalveolar lavage (BAL) is useful because lavage
aliquots are progressively more hemorrhagic. Hemosiderin-laden macrophages may
be demonstrated by Prussian blue staining. BAL is most helpful in the diagnosis
of diffuse pulmonary opacities without hemoptysis. In patients who do not
experience the typical episodes of hemoptysis, lung biopsy is the only unequivocal means of establishing
the diagnosis and may be accomplished by transbronchial or surgical lung biopsy
techniques.
The prognosis in IPH is poor. Children and adolescents
more frequently experience a rapid course and have a worse prognosis. In
adults, the prognosis is more favorable. Corticosteroids and other
immunosuppressive drugs may be effective during an acute episode. Chronic oral
corticosteroids may decrease episodes of acute alveolar hemorrhage and delay
progression to chronic fibrotic changes. In patients with severe respiratory
failure, extracorporeal membrane oxygenation may prolong survival until
immunosuppressive therapy becomes effective. In IPH patients with celiac
disease, a gluten-free diet has been associated with remission of pulmonary symptoms.
