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PAN

posted Mar 5, 2014, 6:19 AM by Ewa Rakowski   [ updated Mar 5, 2014, 6:33 AM ]

A new Monte Minute brought to you by RAT Hyun ah Yoon:

At a past conference we had an interesting case of 41 year old gentleman who presented with acute onset of excruciating abdominal pain and several weeks of fatigue.  Blood pressure was elevated at 188/116, exam revealed diffuse nonfocal tenderness of abdomen, bilateral CVA tenderness and  laboratory results were notable for elevated Cr, ESR, CRP, negative ANCA.  CT abdomen with contrast was done showing infarcts in both kidneys which was subsequently followed by abdominal angiography revealing numerous microaneurysms in multiple vascular territories consistent with a diagnosis of polyarteritis nodosa.

We will briefly go over Polyarteritis Nodosa (PAN) as although a rare disease, we often think about the disease in our differential diagnosis of a range of clinical presentations.

Pathophysiology: Polyarteritis nodosa is an ANCA-negative vasculitis characterized by segmental transmural inflammation and necrosis of medium-sized and small muscular artery walls.

Epidemiology: Peak age of onset is between 40 and 60 years.  There appears to be a 1.5:1 male predominance.

Most cases of PAN are idiopathic, although hepatitis B virus (HBV) infection, hepatitis C virus (HCV) infection, and hairy cell leukemia are important in the pathogenesis of some cases


Clinical Manifestations: Patients with polyarteritis nodosa typically present with fever, arthralgia, myalgia, abdominal pain, and weight loss.  Most patients have peripheral nerve manifestations, most commonly mononeuropathy or mononeuritis multiplex.  Up to one third of patients have renal arteriolar involvement, which presents as renovascular hypertension; glomerulonephritis is not seen. 

Other presenting features include testicular pain, painful cutaneous nodules, skin ulcers, palpable purpura, and livedo reticularis. There is occasional involvement of the coronary arteries. Polyarteritis nodosa rarely involves the central nervous system or pulmonary vessels. Anemia, leukocytosis, thrombocytosis, and elevation in ESR are typically present.



Diagnosis: There are no formal diagnostic criteria for polyarteritis nodosa.

The diagnosis is made on the basis of a constellation of typical symptoms, supportive laboratory tests, and either a biopsy of the affected tissue (i.e., skin, nerve, or muscle tissue — both renal and hepatic biopsies are contraindicated given bleeding risk) showing characteristic necrotizing arterial inflammation or visceral angiography showing microaneurysms in the renal, mesenteric, or hepatic vasculature.  

Laboratory tests are supportive but not diagnostic and may suggest alternative diagnoses.  Inflammatory markers (ie. ESR, CRP) are often elevated but are nonspecific.  The presence of ANCAs against myeloperoxidase or against protease 3 favors the diagnosis of microscopic polyangiitis and granulomatosis with polyangiitis, respectively, whereas low complement levels suggest cryoglobulinemic vasculitis (low C4 levels) or systemic lupus erythematosus (low levels of C3 and C4).

Management : Most patients respond to treatment with high-dose corticosteroids (the equivalent of 1 mg/kg/d of prednisone).  Following several weeks of treatment, the dose can be slowly tapered if clinical and laboratory signs of inflammation have abated.  Cyclophosphamide is indicated for patients who do not respond to corticosteroids or have significant kidney, gastrointestinal, cardiac, or neurologic involvement.

In patients with hepatitis B–associated polyarteritis nodosa, a short course (1 to 2 weeks) of corticosteroids should be given concomitantly with antiviral therapy (such as entecavir).  Using this approach, more than 50% of patients with hepatitis B e antigen–positive polyarteritis nodosa respond with resolution of the arteritis as well as seroconversion to anti–hepatitis B e antibody positivity.

Hypertension is a common manifestation of polyarteritis nodosa that can be effectively treated with ACE inhibitors.

Prognosis: The prognosis for patients with untreated polyarteritis nodosa is grim, with a 5-year survival rate of 13%; death is often a consequence of renal failure, myocardial infarction, or stroke.  With appropriate therapy, the 5-year survival rate is approximately 80%.   

Given the poor prognosis associated with untreated polyarteritis nodosa and the substantial improvement with appropriate treatment, it is important to consider this condition early in the differential diagnosis in order to minimize morbidity and the risk of death. 

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Ewa Rakowski,
Mar 7, 2014, 7:36 AM
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Ewa Rakowski,
Mar 7, 2014, 7:37 AM
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