Which data would be most helpful in diagnosing erythema migrans (Lyme disease) in a teen?

Which data would be most helpful in diagnosing erythema migrans (Lyme disease) in a teen?

• A. The rash is pruritic and feels warm
• B. The adolescent recently went backpacking in wooded area
• C. A sore throat developed 3 days ago
• D. The adolescent went on a hiking trip 3 days ago in Southern California

Answer: (D)

Exposure to tick habitats in regions where Lyme disease is transmitted is what makes the data most informative. Erythema migrans is the early sign of Lyme disease and is linked to bites from Ixodes ticks that live in wooded or brushy areas. So, knowing that the teen spent time backpacking in a wooded area provides the strongest clue that a tick bite could have occurred and that an expanding erythema migrans rash might develop days to weeks later. The rash itself, when present, is usually an expanding red patch that is not itchy and not simply warm to the touch; itching or warmth alone doesn’t reliably point to erythema migrans. The other data are less helpful for establishing Lyme disease. A pruritic and warm-feeling rash is not typical of erythema migrans and could suggest other conditions. A sore throat is nonspecific and not related to this diagnosis. A hiking trip in Southern California carries some exposure risk but Lyme disease is less common there, making this information less contributory to diagnosing erythema migrans in most settings.

Exposure to tick habitats in regions where Lyme disease is transmitted is what makes the data most informative. Erythema migrans is the early sign of Lyme disease and is linked to bites from Ixodes ticks that live in wooded or brushy areas. So, knowing that the teen spent time backpacking in a wooded area provides the strongest clue that a tick bite could have occurred and that an expanding erythema migrans rash might develop days to weeks later. The rash itself, when present, is usually an expanding red patch that is not itchy and not simply warm to the touch; itching or warmth alone doesn’t reliably point to erythema migrans.

The other data are less helpful for establishing Lyme disease. A pruritic and warm-feeling rash is not typical of erythema migrans and could suggest other conditions. A sore throat is nonspecific and not related to this diagnosis. A hiking trip in Southern California carries some exposure risk but Lyme disease is less common there, making this information less contributory to diagnosing erythema migrans in most settings.