Simple cases
Case 49
61-year-old lawyer with itchy rash on arms and trunk.
History
How long have you had this?
The itching started 3 days ago. When I looked, I had all these spots.
This dermatosis starts acutely and is intensely pruritic.
Where you sick when the itching started? Had you had fever or fever blisters?
No. I am never sick. I felt great.
Good question which helps with differential diagnostic considerations, but in this case doesn't advance our search.
Do you have pets?
Yes, we have a dog and two turtles.
Another crucial question. When you suspect arthropod bites, always ask about pets. In this case, not relevant.
Had you been abroad before this started?
Yes, I just got back from Prague.
Could be useful, but once again, not here.
Did you have sexual contacts in Prague?
No, not at all.
Nothing here suggests a sexually transmitted disease and the question may annoy the patient.
Were you working in the garden before this started?
Yes, I had to stack our firewood. I always do it in the fall. I think I had spots like this once before after working with the wood piles.
This is the key question, and the answer points you straight toward the diagnosis.
Lesion
Choose the right efflorescences:
False. A nodule is > 1cm.
Hives are transient.
These are classic erythematous papules- palpable lesions < 1 cm.
Macules are flat; these lesions are raised.
Diagnosis
Choose the right diagnosis:
There is no history for a drug reaction.
Prurigo is usually a subacute or chronic disease. An individual lesion could fit with prurigo simplex subacuta but not the overall picture.
There is no history of sexual contact. While secondary syphilis has many faces, the cutaneous lesions hardly ever itch.
The history and the distribution of lesions do not fit at all.
The history is perfect. Larva of the mite Trombicula autumnalis wait on grasses, shrubs and wood, looking for a blood meal before the winter. Clinically pruritic papules on both exposed and covered areas are seen.
Therapy
Choose the right therapy(ies):
The mite larva are found outside, not in the house.
Correct. The best way to treat the itch
By the time the itching starts, the mites have long left the skin, so this approach is not sensible.
Clearly the best prophylactic measure.
