Picture Quiz
Case history
A 38 year old Asian American woman
comes to the office with a red painful ankle.
The patient states that she sprained her
right ankle two days ago by inverting it
while walking. She believed it to be a minor
sprain and did not go to a physician.
However, she did apply a Chinese medicine
patch that was given to her by her mother,
who recently emigrated from China. The
patient applied the medicine that was
impregnated in a patch to the anterior
medial and lateral portions of her ankle,
leaving the posterior portion uncovered.
The following day the patient broke out in a
red and painful rash with blisters. The
patient denies any fever or systemic symptoms. She does not know the ingredients in
the medication. The rash is painful and the
lesions made it painful to walk. Figures 1
and 2 show the patient's ankle at the time of
her first visit to the office. The erythema has
a well demarcated border, which has been
traced by the doctor's pen in both figures.
The skin is also covered with many small
vesicles (<5 mm in diameter) and at least
five large intact bullae (>5 mm in diameter).
Fig 1 |
|
Fig 2 |
|
Questions
- What is the most likely diagnosis?
- How would you confirm this diagnosis?
- What features of this rash distinguish it from other conditions in the differential?
- How would you manage this patient?
Answers
- Severe contact dermatitis to topical Chinese medicine.
- Recent history of exposure to allergen and physical examination revealing a classic pattern of contact dermatitis - erythema with a well demarcated border, vesicles and bullae.
- Lack of a linear pattern distinguishes this from a contact dermatitis to a plant, and the presence of vesicles makes an irritant dermatitis less likely.
- Discontinue use of Chinese medication; prescribe cold compresses and topical steroid preparations. If the patient shows no improvement after a two day follow up, oral prednisone should be considered. (In this actual case, the patient was given a
two week course of prednisolone starting with 60 mg daily and tapering down to 5 mg daily. The patient responded rapidly and the condition fully resolved.)
Discussion
Allergic contact dermatitis is a delayed hypersensitivity reaction that occurs after exposure to
an antigenic substance. This dermatitis usually
appears as an acute vesicular dermatitis within
a few hours to 72 hours after contact. The
course peaks within 7 to 10 days and resolves
within 21 days if there is no repeat exposure.
This patient has a severe contact dermatitis to
the topical Chinese medicine. It is possible that
the patient was exposed to this substance as a
child in China. Although this patient reports no
previous occurrences of contact dermatitis, the
recent history and physical examination represent a classic pattern for contact dermatitis.
Therefore no further testing is indicated.
Because the ingredients of the Chinese medicine are unknown, it is difficult to pinpoint the
exact allergen causing the contact dermatitis.
Differential diagnosis
The differential diagnosis includes irritant dermatitis and contact dermatitis due to other substances. The prototypical contact dermatitis is poison oak, ivy, or sumac. These conditions can
look similar and are often distinguished by the
line of vesicles that can occur from brushing
against one of the plants of the Anacardiaceae
family. Also the linear pattern occurs from
scratching oneself and dragging the oleoresin
across the skin with the fingernails. In the case
presented here, the erythema and vesicles are
widespread and show no linearity.
Although irritant dermatitis may look like
contact dermatitis it is not caused by an
immunological mechanism. The causative
substance in irritant dermatitis (a harsh detergent, for example) is purely irritating to the
skin and does not serve as an allergen. In
patch testing strong allergic reactions are
vesicular whereas irritant reactions show a
non-vesicular erythema.
Treatment
The aetiological agent must be identified and
removed. Cold wet compresses may be prescribed for the open areas where bullae and
vesicles have broken open. Compresses are
valuable to relieve symptoms during the acute
blistering stage. They may be applied for 15 to
30 minutes several times a day. A strong topical corticosteroid may be used to treat the
severe inflammatory reaction. Topical steroids
are not effective in penetrating blisters but
may be very valuable for the surrounding
areas. Oral antihistamines may be given for
itching. Aveeno baths may be used to soothe
the area and control itching. If use of systemic
steroids is indicated (in severe cases or those
refractory to topical steroids), there is a choice
of oral prednisolone or an injection of triamcinolone acetonide (40 mg intramuscularly).
Oral prednisolone doses may vary widely. A
simple dose regimen is 20 mg twice a day for
at least six days.1 Antibiotic therapy is required
for cases involving secondary infections.
First published in: Western Journal of Medicine 2000;171:361-362.
This picture quiz was compiled by Dana Howard and Richard Usatine, UCLA, 200 Medical Plaza, Suite 220, Los Angeles, CA 90095-1628
Correspondence to: Dr Usatine rusatine@ucla.edu
studentBMJ 2000;08:303-346 September ISSN 0966-6494
- Habif T. Clinical Dermatology: a color guide to diagnosis and therapy, London: Mosby, 1996. 3rd ed.
