Simple cases
Case 21
26-year-old student is referred with a red area on the right arm and axilla.
History
Do you have joint pains or fever?
No, but I am really tired.
Further symptoms can help with the diagnosis.
Do you have pets?
Yes, a parakeet.
A potentially useful question, but not helpful in this case.
Do you sweat a lot?
No.
Sweating might be a trigger based on the location.
How long have you had this lesion?
For 3 weeks.
The time course can provide clues to the etiology.
How did the lesion start?
At first it was a little red spot, like a insect bite, then it started to grow and grow.
The dynamics of a lesion often gives clues as to the etiology.
Do you take any medications?
No.
One of the most important questions in medicine. A drug reaction in the form of the baboon syndrome could look like this.
Have you ever had a tick bite?
No.
Another good question looking for possible causes.
Have you worn any new pieces of clothing?
No.
Fabrics with excess dyes or stiffeners can cause irritant contact dermatitis if worn before they are washed. Here the history does not support this possibility.
Lesion
Choose the right efflorescences:
Lichenification is secondary to rubbing and features exaggerated skin markings.
This lesion is macular because it is flat. Since it is large and red, erythema is the usual descriptive term.
There is no loss of skin substance.
Poikilodermia consists of telangiectases, atrophy and pigmentary changes. All are missing here.
Hives result from dermal edema. They are not seen here.
Diagnosis
Choose the right diagnosis:
As the name suggests, a spreading erythema.
Erysipelas is warm, acute and the patient is sick.
Tinea corporis is another spreading annular erythema, but the lesion has peripheral scale.
Scale, lichenification and pruritus are missing.
Erythrasma is not an annular erythema with prominent border. It shows a coral red fluorescence with Wood light examination.
Therapy
Choose the right therapy(ies):
This is the treatment for gonococcal urethritis, not erythema chronicum migrans.
This regimen is designed for borrelial carditis or meningitis, not for erythema chronicum migrans alone.
This is the appropriate treatment for erythema chronicum migrans.
This is a possible systemic treatment for scabies.
This is another acceptable regimen, which is especially applicable during pregnancy.
