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A 59 year old woman with an eight year history of seropositive erosive rheumatoid arthritis (RA) receiving sulfasalazine and penicillamine presented with severe sudden onset pain radiating from the left elbow to the left thumb, index and middle fingers. Examination disclosed synovitis of the left wrist, which might have caused median nerve compression. The wrist joint was injected with 20 mg of triamcinolone acetate with 1% lidocaine (lignocaine). She returned the following morning complaining of worsening pain. She was clinically well with no fever. White cell count was normal, but the erythrocyte sedimentation rate (ESR) was raised at 73 mm/1st h. A transcutaneous nerve-stimulating (TENS) machine was applied and she was prescribed amitriptyline 25 mg at night. The following day she had improved significantly but had developed a vesicular rash in the C6 dermatome consistent with herpes zoster infection (fig 1). Viral titres were consistent with current varicella zoster infection.
Establishing the cause of pain in patients with RA can be notoriously difficult. In addition to the psychological factors that influence pain perception, wrist and hand pain may result from rheumatoid synovitis, soft tissue inflammation, or mechanical nerve compression at wrist, elbow, and cervical spine.
Herpes zoster infection is heralded by burning discomfort in a dermatomal distribution, which may occur for up to five days before the onset of the typical rash. Cervical dermatomes are affected in up to 15% of patients1 and may result in diaphragmatic paralysis and lower motor neurone paresis.2 In this case the occurrence of prodromal symptoms of herpes zoster mimicked the symptoms of carpal tunnel syndrome, presumed secondary to RA synovitis.
RA increases the risk of herpes zoster infection.3 In one series the use of low dose methotrexate, long duration of disease, and seropositivity were risk factors for subsequent infection.4 Gold treatment may also increase the likelihood of shingles.5
Immunocompromised patients should receive acyclovir early to avoid viral dissemination. In patients with RA the complexity of the differential diagnosis may delay diagnosis unless the possibility of herpes zoster infection is kept in mind.
Conflict of interest: none.
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