Polyarteritis nodosa is an uncommon connective tissue disorder, characterized by involvement of small and medium sized arteries. There is necrotizing vasculitis with polymorphonuclear infiltration, necrosis and aneursymal dilatation of the vessel wall.
The involvement of vessels is widespread and involves major organs except pulmonary vessels. It is a rare disease which commonly manifests in adult age, men being affected more than women.
Aetiology
The exact aetiology of the Polyarteritis nodosa disease is not known. Immunoglobulins and complements have been located in the vessel wall of the patients of PAN, supporting their role in its etiology.
There is high incidence of hepatitis B surface antigen (HBs Ag) in the blood and circulating HbsAg – anti-HBs immune complexes in the sera of patients as well as demonstration of hepatitis B antigen, 1gM and complement in the blood vessel wall, suggesting the role of immunologic basis of the disease.
Clinical features
These are extremely variable and non-specific in the case of Polyarteritis nodosa. Fever, malaise, weight loss, anorexia, abdominal pain and headache are the commonest symptoms. When any particular organ is involved, symptoms are referable to that.
Thus involvement of kidney leads to glomerulonepheitis, hypertension, renal failure, muscular skeletal system involvement leads to (myalgia, arthritis) nervous system (seizures, CVA, peripheral neuropathy) gastrointestinal tract (abdominal pain, nausea and vomiting, Bowel infarction, bleeding, perforation).
Heart (congestive heart failure, myocardial infarction, pericarditis) and skin (rash, purpura, Raynaud’s phenomenon) and involvement of lungs leads to asthma-like picture. Hepatic necrosis and cholecystitis, retinal hemorrhages, gangrene of the extremities are other features of vascular involvement.
Polyarteritis nodosa involves almost all the major organs. It may be of acute onset or may arise in an insidious manner. In most cases there is protracted course with flare up of activity. Some symptoms like hypertension may persist even after control of the acute process.
Investigations
There is elevation of ESR with rise in leucocyte count. Urine may show protinuria and hematuria. Hypergamma globulinaemia may be present and in 30% of patients Hepatitis B surface antigen is positive.
Arteriograms of the affected organ will show micro aneurysms in small and medium sized vessels especially in the kidney, liver and intestines.
Biopsy of the affected organ will show acute necrotizing inflammation beginning in the intima and inner portion of the media and extending to involve entire thickness of the vessel wall. There are fibrinoid deposits along with inflammatory reaction, destruction of the internal elastic lamina leading ultimately to thrombosis.
Diagnosis
Diagnosis of Polyarteritis nodosa is mainly based on clinical picture and investigations like biopsy.
Treatment
Untreated cases of Polyarteritis nodosa follow a downhill course. Death usually results from renal failure, gastrointestinal complications and cardiovascular complications. Corticosteroids are the main line of treatment. Predinsolone is given in a dose of 1-2 mg/kg/day in divided doses. This has to be given a period of 4-6 weeks and then patient put on maintenance dose.
In patients with various organ involvements and not responding to steroids, immuno suppressive drugs are employed. Cyclophosphamide (1-2 mg/kg! day) in divided doses is beneficial especially when combined with steroids.
