A 77-year-old woman gave a 10-day history of pain and weakness in her arms and legs, worsening over 12 h. Her muscle aching in the neck, shoulders, back and limbs progressed over the next 48 h; her limbs weakened, and she became unable to walk. She reported intermittent abdominal pain, and had recently lost 12 kg of weight. She had no joint pain or swelling, headache, fever, breathlessness, visual disturbance, bladder or bowel dysfunction. She had travelled to Turkey 3 months before, but was well while away with no insect bites.

She had a history of biopsy-proven nodular prurigo and a vestibular schwannoma under observation since 2013. Before admission, she had been very active and took no medications. She was a carer for her husband, and drove her grandchildren to school. There was no relevant family history.

On examination, she was in severe pain. The proximal limb muscles were tender to palpation. Tone was normal. There was symmetrical proximal weakness in all four limbs with a give-way component. Reflexes were present, and plantars were flexor. Coordination and sensation were normal. She had a soft systolic murmur, but respiratory and abdominal examinations were normal. She had several skin lesions on her arm, previously diagnosed as nodular prurigo. The joints were normal.

Investigations included an erythrocyte sedimentation rate of 35 mm/1st h (<30). White cell count was elevated at 17.1×10⁹/L (4.0–11.0) with neutrophilia. Her eosinophilia (1.67×10⁹/L (0.04–0.40)) was first noted 6 months before, initially at 0.76×10⁹/L, rising over the ensuing months. Serum C reactive protein was raised at 113.2 mg/L (<10) from normal 6 months before. Liver function was abnormal with elevated serum alkaline phosphatase (301 units/litre (U/L) (45–105)), gamma-glutamyl transferase (341 U/L (4–35)), alanine aminotransferase (133 U/L (5–35)), but normal aspartate aminotransferase and bilirubin. Rheumatoid factor was initially raised at 173 IU/ml (<30), but later fell to …