John was 14 years old when he was referred by his general practitioner (GP) with generalised stiffness in his legs and wrists for the past 4 days. His GP noted that his temperature was 39.5°C and had been raised for 2 days. John also complained of having had a frontal headache the previous day which had now resolved.

There was minimal past medical history though John had been diagnosed with ocular hypertension 2 years prior to current presentation which was currently being monitored; however, he was not on any ongoing treatment for this.

John had no known contact history and his immunisations were up to date. His mother was Japanese and his father was Caucasian.

On examination John was alert and orientated. His conjunctivae were both injected but they were not itchy or painful and there was no exudate. John had a cold sore on the right side of his mouth, which appeared to have almost resolved. His lips were not red but were peeling (fig 1). There were no intra-oral ulcers. He was noted to have minimal cervical lymphadenopathy on the right.

John’s throat was noted to be “pink” with no tonsillar enlargement or exudate.

John’s blood pressure was 121/74 mmHg and his temperature was 39.2°C.

His chest was clear and heart sounds normal.

His neurological examination was normal with no neck stiffness.

John’s wrists and lower legs were both stiff. His right knee appeared swollen and had limited flexion and extension. His right ankle had limited range of movements but no swelling. On his left leg there was a 3 cm × 4 cm erythematous region which was not tender or itchy. Within this area there was a smaller raised area which blanched. There were three smaller similar lesions on his …