What is Allergic (eosinophilic) granulomatous angiitis (Churg-Strauss syndrome)?
This rare disease has been described in detail by J. Churg and L. Strauss, and in some publications is called by their names. It is considered as one of the subgroups of the classic nodular polyarteritis, revealing in many respects identical clinical and morphological manifestations. In particular, acute necrotic arteritis of small and medium caliber is histologically characteristic of both diseases. However, allergic granulomatous angiitis has a number of characteristic differences, which suggest the participation of other pathogenetic mechanisms in its development. These differences include:
- more frequent lesion of small vessels;
- the presence of inside and extravascular granulomas, which usually have a diameter of about 1 mm or more and are located near the small arteries or veins. They consist of a central necrotic nucleus (containing destroyed cells and altered collagen fibers) and macrophages radially surrounding it, giant cells and especially eosinophils (which is more pronounced in the early stages), and to a lesser extent neutrophils and lymphocytes;
- high eosinophilia in peripheral blood, bone marrow and perivascular infiltrates in various organs;
- significant frequency of bronchial asthma and pulmonary pathology.
Arteritis, eosinophilic granulomas and infiltrates can be localized in almost any organs and tissues, which leads to a polymorphic clinical picture similar to that in nodular polyarteritis. Most often granulomas are found in the skin and pericardium.
Causes of Allergic (eosinophilic) granulomatous angiitis (Churg-Strauss syndrome)
The etiology and pathogenesis of this variant of vasculitis is unknown. It can be assumed that type I immunopathological reactions are involved on the basis of persistent eosinophilia and frequent increases in IgE levels. The level of complement in the blood is normal. The increased content of circulating immune complexes in serum and the deposition of IgM and C3 in the renal glomeruli were observed only in a few patients and, apparently, is not significant.
Symptoms of Allergic (eosinophilic) granulomatous angiitis (Churg-Strauss syndrome)
The disease begins at the age of 15-70 years, more often around 40-45 years. The ratio of men and women is the same as with nodular polyarteritis (3: 1). An important feature of the clinical picture is a rather long (several years) prodromal phase, manifested by symptoms of bronchial asthma, which is often preceded by allergic rhinitis. The peculiarity of these manifestations lies in the fact that they often develop in middle-aged people among people who do not have similar diseases among their relatives. The second phase is characterized by high eosinophilia in peripheral blood and transient pulmonary eosinophilic infiltrates (Leffler syndrome). These manifestations may also recur for several years, but then they are replaced by the 3rd phase, i.e., the clinical picture of vasculitis proper, which is very close to polyarteritis. The first symptoms of the addition of systemic vasculitis are often fever and rapid weight loss.
The clinical features that distinguish allergic granulomatous angiitis from classical polyarteritis are given below.
- More frequent and severe lung damage. In addition to the volatile spotted eosinophilic infiltrates noted above, the development of bilateral large nodal infiltrates and diffuse interstitial pneumonitis is possible. The disintegration of the lung tissue with the formation of cavities and bleeding is uncharacteristic.
- Cardiac pathology such as endothelial fibrosis, eosinophilic infiltrates and nodular pericarditis, which is not characteristic of polyarteritis, is why an echocardiographic study is necessary.
- More frequent skin changes, especially hemorrhages such as purpura and nodules.
- More rare gastrointestinal bleeding and intestinal heart attacks (despite the same frequency of abdominal pain syndrome).
- Less severe kidney damage. Renal failure develops rarely. With the help of biopsy, focal necrotic glomerulonephritis is detected; proper arteritis and the formation of helomonus are recorded infrequently.
- A very rare sign of the disease can be eosinophilic granulomas of the prostate gland and urinary tract, which sometimes leads to a delay in urine excretion.
Diagnosis of Allergic (eosinophilic) granulomatous angiitis (Churg-Strauss syndrome)
Among laboratory parameters, eosinophilia is first of all characteristic of 90% of patients. The content of eosinophils (mostly mature forms) often exceeds 50%, and in absolute figures it can reach 20 · 109 / l. At the same time, common leukocytosis is often noted – at the onset of the disease up to 60 · 109 / l. ESR is usually elevated, RF is rarely found and in low titers. It is noteworthy that, in contrast to polyarteritis nodosa, there is no combination of signs of infection with the hepatitis B virus with allergic granulomatous angiitis.
The diagnosis is based on the very characteristic clinical, laboratory and histological features discussed above. It is very important to have a history of bronchial asthma, which is replaced by a systemic disease. In the polymorphic picture of the disease, skin nodules are diagnostically significant, circulatory failure, non-decaying pulmonary infiltrates, high eosinophilia, increased IgE levels. In doubtful cases, a biopsy of the affected tissues or organs (skin, lungs, kidneys, prostate gland) is necessary, allowing to detect the characteristic combination of vasculitis, eosinophilic infiltration and necrotic granulomas. From allergic granulomatous angiitis, it is necessary to distinguish completely benign and rapidly reversible (although sometimes recurrent) eosinophilic pneumonia, which is not characteristic of the features of a systemic disease. In some cases, the question of differentiation with Wegener’s granulomatosis arises. In such cases, it must be borne in mind that although rhinitis (allergic) is very common in allergic granulomatous angiitis, severe granulomatous infiltration (especially with tissue destruction traits) is completely uncharacteristic to it, being the most important symptom of Wegener’s syndrome. Sinusitis, the formation of cavities in the lungs, hemoptysis, the appearance of ulcers in the mouth, and frequent eye damage are also in favor of the latter.
Treatment of Allergic (eosinophilic) granulomatous angiitis (Churg-Strauss syndrome)
Most authors believe that allergic granulomatous angiitis is easier to treat with relatively high doses of prednisone (40-60 mg / day) than classical polyarteritis. At the same time, after the termination of hormone therapy, relapses are not uncommon. Therefore, in addition to corticosteroids, it is also advisable to include cyclophosphamide in the treatment complex, that is, to apply the same method of therapy as in case of polyarteritis. In particular, A. Pauci et al., Who have extensive experience in the treatment of systemic vasculitis, consider it justified to assign cyclophosphamide in allergic granulomatous angiitis to either seriously ill patients from the onset of the disease or to those whose corticosteroid monotherapy does not give sufficient effect.