A young woman with fever of unknown origin

A 33-year-old woman presented with a 2-month history of moderate-grade fever associated with chills, headache and diminished appetite. She had lost 8 kg since the onset of illness. Clinically, she had fever (temperature 38.5° C), but the rest of the general physical and systemic examinations were normal. Investigations revealed an erythrocyte sedimentation rate (ESR) of 80 mm after 1 h. Routine haemogram, blood smear for malarial parasite, urine microscopic examination, urine culture, blood culture, chest X-ray and ultrasounds of abdomen and pelvis were noncontributory. Mantoux test was negative. She was initially treated empirically for malaria with chloroquine and subsequently with ciprofloxacin for enteric fever with no response. On repeated clinical examinations she was detected to have small, diffuse, nontender thyromegaly. A 131-radioiodine scan revealed markedly low uptake of tracer. Radioactive iodine uptake (RAIU) was negligible at 24 h. Serum tri-iodothyronine (T3) was 180 ng/dl (normal 60–181), serum thyroxine (T4) 10 μg/dl (normal 4.5–10.9) and thyroid-stimulating hormone (TSH) 0.4 μU/ml (normal 0.5–5.0).