Clinical Image: Splinter hemorrhage as a diagnostic clue of muscular polyarteritis nodosa

The patient, a 59‐year‐old woman with a history of anorexia who was a nonsmoker and took no medication, presented to our clinic following 4 weeks of fever, acute burning paresthesia, pain, numbness, and muscle weakness of both lower and upper limbs. Her body weight had decreased by 6 kg during the previous 4 weeks. Physical examination results revealed myalgia and muscular tenderness of the lower extremity. C‐reactive protein (CRP) and creatine phosphokinase (CPK) levels were elevated at 5.77 mg/dl; (normal value, <0.3 mg/dl) and 365 U/L (normal value, 40‐150 U/L), respectively. Magnetic resonance imaging (fat‐suppressed T2 imaging) of the lower legs demonstrated high intensity in bilateral crural muscle, suggesting widespread muscular inflammation (A). A nerve conduction study revealed asymmetrical sensorimotor axonal neuropathy, suggesting mononeuritis multiplex. The physical examination was also significant for “splinter hemorrhages” at the distal fingernails (B, white arrows). The hemorrhage is evidence of the disruption of the delicate spiral arteries of the nail bed. Clinicians should consider a broad differential diagnosis including antiphospholipid syndrome, vasculitis, drug reactions, infective endocarditis, and renal failure as potential causes of splinter hemorrhages (1). A biopsy specimen from the crural muscle demonstrated inflammation and elastic fibers destruction in a medium‐sized muscular artery (C, white arrow). The patient was diagnosed with polyarteritis nodosa. Treatment with prednisolone and intravenous immunoglobulin was initiated, and azathioprine was later added. Following treatment, all digit, nail, and muscle involvement recovered with normalization of CRP and CPK levels. Clinicians should remember to consider that splinter hemorrhage can be a diagnostic clue of vasculitis, even among patients presenting with muscular symptoms and imaging findings of myositis.