What is the diagnosis and treatment approach for a patient with suspected polyarteritis nodosa, particularly one with a history of hepatitis B infection and symptoms such as fever, fatigue, weight loss, and abdominal pain?

Polyarteritis Nodosa: Diagnosis and Treatment

Immediate Diagnostic Approach

For a patient with suspected polyarteritis nodosa (PAN), particularly with hepatitis B infection and systemic symptoms, obtain tissue biopsy from the most accessible symptomatic site and abdominal vascular imaging to confirm diagnosis before initiating treatment. 1, 2

Key Clinical Features to Assess

• Neurologic involvement: Examine for mononeuritis multiplex or peripheral neuropathy (present in 50-75% of cases) 3
• Cutaneous manifestations: Look for skin nodules and livedo reticularis 2
• Gastrointestinal involvement: Assess for abdominal pain and signs of mesenteric ischemia 2
• Renal manifestations: Check for hypertension and renal insufficiency 2
• Constitutional symptoms: Document fever, fatigue, and weight loss 1, 2

Diagnostic Testing Algorithm

Tissue confirmation is preferred over imaging alone 1:

• For skin involvement: Obtain deep skin biopsy (not superficial punch biopsy) to capture medium-sized vessels 2
• For suspected visceral involvement: Perform abdominal vascular imaging (CT or MR angiography) to identify saccular/fusiform aneurysms and stenotic lesions in mesenteric, hepatic, and renal arteries 2
• Histologic findings: Look for mixed-cell inflammatory infiltrates, fibrinoid necrosis, and absence of granulomas 1

Critical caveat: Since this patient has hepatitis B, test for HBsAg and HBeAg status immediately, as HBV-associated PAN requires fundamentally different treatment than idiopathic PAN 4, 5

Treatment Strategy Based on Disease Subtype

For Hepatitis B-Associated PAN

Treat with antiviral therapy (lamivudine or similar) combined with plasma exchange and short-term corticosteroids, NOT cyclophosphamide-based immunosuppression 4, 5:

• Plasma exchange removes circulating immune complexes 4
• Antiviral therapy addresses the underlying trigger 5
• Short-term corticosteroids control acute inflammation 4
• Monitor for HBeAg seroconversion as marker of treatment response 5

For Idiopathic Severe PAN (if HBV-negative)

Initiate treatment with cyclophosphamide and high-dose glucocorticoids immediately 1, 2:

• Glucocorticoid administration: Use intravenous pulse glucocorticoids over high-dose oral glucocorticoids for severe disease 1, 2
• Cyclophosphamide is strongly preferred over rituximab for newly diagnosed severe PAN 1
• Do NOT add plasmapheresis to cyclophosphamide and glucocorticoids in idiopathic PAN (no added benefit) 1

Disease Severity Classification

Severe disease includes life-threatening manifestations such as:

• Mesenteric ischemia requiring surgery 5
• Progressive renal insufficiency 2
• Extensive neurologic involvement 3
• Cardiac involvement 3

Non-severe disease can be treated with non-cyclophosphamide immunosuppressive agents (methotrexate or azathioprine) plus glucocorticoids 1

Maintenance and Long-term Management

After Achieving Remission

Transition from cyclophosphamide to a less toxic agent (methotrexate or azathioprine) once remission is achieved 1, 2:

• Continue non-glucocorticoid immunosuppressive therapy for 18 months total 1
• Taper glucocorticoids based on clinical response (optimal duration not well-established, but guided by disease activity) 1
• Discontinue immunosuppression after 18 months if sustained remission 1

Monitoring for Relapse

• Relapses occur in 28% of idiopathic PAN cases, typically within 26 months of diagnosis 4
• Use serial neurologic examinations (not repeated EMG/NCS) to monitor peripheral neuropathy 2
• Repeat vascular imaging if new symptoms suggest relapse 1

Special Consideration: Genetic Forms

If patient is young with recurrent strokes or early-onset disease, test for adenosine deaminase 2 (ADA2) deficiency 1, 4:

• This monogenic form requires TNF inhibitors as primary treatment 1
• TNF inhibitors prevent ischemic CNS complications 4
• Do NOT treat with glucocorticoids alone 1

Prognosis

Untreated severe PAN carries 40% mortality at 5 years, but with appropriate treatment, 5-year survival improves to 83% 2, 4. The distinction between HBV-associated and idiopathic PAN is critical, as treatment approaches are fundamentally different and using immunosuppression in HBV-associated disease without antiviral coverage can worsen outcomes.