Chapter 20: Autoimmune diseases, Polyarteritis Nodosa, Rheumatic Fever, Wegner’s granulomatosis
Polyarteritis Nodosa is a disease that is characterized by swelling of the medium-sized vessels, associated with fibrinoid necrosis and inflammatory infiltrate representing non-infectious necrotizing vasculitis. As a result, there is aneurysm formation and vessel occlusion.
Age: – Mostly seen in middle age.
Sex: – More common in males.
Sign and symptoms
- A renal angiogram shows an aneurysm.
- It is a life-threatening condition with end-stage renal failure in 30% and other complications are malignant hypertension and cerebrovascular accidents.
Pathogenesis: – It is unknown. It may be due to hypersensitivity to:
- Drugs like sulphonamide, phenylbutazone, and thiazide.
The mechanism of injury is a type III hypersensitivity reaction.
The affected vessels show fibrinoid necrosis of the vessel wall with intense infiltrate of lymphocytes, plasma cells, and macrophages.
There is symmetrical involvement, which gives a nodular aneurysm called Nodosa. Common complications are thrombosis and infarction.
- Renal angiogram.
- Muscle biopsy may be diagnostic to see vascular changes.
- There may be raised ESR, CRP positive and rarely raised Immunoglobulin.
- A minority of the patients show pANCA(antineutrophil cytoplasmic antibodies).
Aggressive therapy with corticosteroids and cytotoxic drugs are needed to control the disease.
With aggressive therapy 5 years, survival is more than 60%.
Rheumatic Fever may be:-
This is a disease of children.
Characteristic of Rheumatic Fever
- There is a fever.
- Majority show polyarthritis of larger joints.
- There may be carditis.
- There is a subcutaneous nodule called Aschoff’s Bodies. These consist of necrosis, pleomorphic cellular infiltrate, and Aschoff’s Cells.
- There is an erythema marginatum of skin.
- The patient may show Sydenham’s chorea.
- It usually follows H/O pharyngitis due to streptococcus group A, appears after 3 weeks of infection.
Etiology and Pathogenesis
- Direct infection: – But this possibility is ruled out because the lesion is sterile.
- This may be due to streptococcal toxins. Streptolysin Sis not immunogenic. Streptolysin SO is immunogenic and it may form Anti-SO Ab which form (SO + Anti-SO) immune complexes. Myocardium competes for Ig and these complexes deposits there.
- Cross-reacting Ab: – The antibody against streptococcal M-protein may cross-react with cardiac muscles.
Mechanism of Injury
It is a type III immune-complex disease.
In some cases, only the kidney is involved. It starts as acute and becomes a chronic disease.
The earlier lesion is Aschoff’s Body. These are seen in the interstitium of the myocardium close to coronary arteries. Mitral and aortic valves are commonly involved. The cause of heart failure in acute cases is not known.
In some cases, lungs may be involved and patients may develop pleurisy. Arthritis does not cause crippling disease in the patient.
In the kidney, there is diffuse proliferative glomerulonephritis occasionally with crescent formation.
The complication of rheumatic fever is chronic heart disease and poststreptococcal glomerulonephritis.
- There is a past history of streptococcal infection (Sore-throat).
- Raised antistreptolysin O level (ASO).
- Titers of ASO will be raised. Its low concentration may be seen in normal children.
- There is a leucocytosis.
- There is typically raised ESR and CRP positive.
This is a systemic vasculitis, associated with a granulomatous lesion in the upper and lower respiratory tract usually preceding the onset of glomerulonephritis. This condition was first described by Friedrich Wegener.
It is seen in late middle-aged males and the elderly.
It is more common in males.
Etiology and Pathogenesis
- This is more common in HLA-DR2 and there is increased relative risk 3-4 times.
- In the patients, there are ANCA-antineutrophil cytoplasmic antibodies. The main debate at present regarding the various types of ANCA is whether they are involved in the disease process or are generated secondarily.
- Respiratory lesions may lead to epistaxis or hemoptysis.
- Constitutional systems like fever, malaise, and weight loss reflect the systemic nature of the illness.
- Typically there is focal, proliferative glomerulonephritis often associated with necrosis and crescent formation.
- The respiratory tract shows granuloma, which consists of necrosis, infiltration by lymphocytes and macrophages, and multinucleated giant cells.
- Biopsy from the respiratory tract shows granuloma.
- The measurement of cANCA is specific and can be used to know the response to treatment.