The patient
This 16-year-old schoolgirl had started to noticed her joints had become painful over the previous two days. The interphalangeal joint of her middle finger was particularly uncomfortable but the little finger appeared more swollen. Taking paracetamol had not made a great deal of difference. There were no other painful joints, and she did not feel systemically unwell. Her history was unremarkable apart from a borderline vitamin D level for which she was taking supplements.
First instinct
There was definitely redness and swelling in relation to the joints on the third and fifth fingers and yet, interestingly, there was no major pain on palpation of the joints themselves. That was unexpected.
Differential diagnosis
• Systemic lupus erythematosus (SLE)
• Chilblains
• Erythema multiforme
SLE certainly occurs most commonly in women between 16 and 55. Its multisystem effects include an arthritis that may occur in around 50% of affected individuals. At the onset, there is often a constitutional upset. The joints affected looked red and were painful but the patient was otherwise well. Lupus seemed a little unlikely.
Chilblains are painful and result from rewarming too quickly after cold exposure. The extremities are most often affected. The lesion may manifest with redness followed by burning and itching. Deeper lumps may form or there may be superficial lesions with a maculo-papular appearance. They may blister. There was a suspicion of a split in the skin distal to the proximal interphalangeal joint of the middle finger.
Erythema multiforme tends to be symmetrical with hands and feet commonly affected. Initially the lesions are macular and then the characteristic target appearance develops. In 50% of sufferers there may be a mild illness prior to the rash developing. No target lesions were visible here and there was a lack of symmetry.
Getting on the right track
Although the lesion on the middle finger looked flat, the little finger looked swollen. When I palpated it, the soft tissues in the swelling felt firm. This suggested chilblains was the most likely diagnosis. There is no doubt about the recent cold spell but was this the whole story? Finally I asked if her hands had been particularly cold at any time recently. It turned out she had been in a snowball fight without gloves. I suspect that the lure of warmth after the fight had been too tempting and that she had allowed her hands to warm up too quickly.
Snapshot
