Myositis as the initial presentation of panarteritis nodosa.

A 47-year-old man presented with weight loss, bilateral calf pain, fever, hypertension, orchitis and oligoarthritis. Lab tests: anemia and elevated muscle enzymes. Resonance magnetic imaging: hyperintensity in gastrocnemius muscles (myositis). Histologic exam of the muscles: inflammatory infiltrate with atrophy and perifascicular regeneration. Treatment: methylprednisone (bolus) and cyclophosphamide. Muscle pain and swelling and difficulty in walking are common in panarteritis nodosa (PAN), whereas histologically demonstrated myositis is not. Even more rare is myositis as the initial presentation of this vasculitis.