Case 21

Published on 18/02/2015 by admin

Filed under Allergy and Immunology

Last modified 18/02/2015

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CASE 21

Ten-year-old Jimmy is brought to your office by his mother the day after he returned from summer camp, with diffuse blisters over his arms and legs. He has never had these before, and there is no family history of autoimmune disorders. He is not febrile and has taken no medications. Other than these blisters, which are associated with moderately itchy skin, he does not feel ill. How do you determine the underlying cause of the problem and how do you treat it?

QUESTIONS FOR GROUP DISCUSSION

1. List some autoimmune disorders that would present in this manner.

2. Given the absence of a family history of blistering disease, travel history becomes very significant. This child has been at “summer camp.” Contact with the leaves of some plants can result in blistering in the sensitized individual. Name one common plant to which contact sensitivity is common. What is the antigen that is causing this problem?

3. Explain why this would need to be a re-exposure and not the result of an initial contact.

4. The summer camp history strongly suggests this is the result of re-exposure to urushiol, a small molecule present in the leaves of the poison ivy plant. Urushiol functions as a hapten following binding to a carrier protein. Define the terms hapten and carrier protein.

5. Describe the etiology of a type IV hypersensitivity reaction. Include in your description each of the following terms: dendritic cells, naive CD4⁺ T cells, memory CD4⁺ T cells, cytokines, macrophages, inflammatory mediators.

RECOMMENDED APPROACH

Implications/Analysis of Family History

There is nothing presented in this case that would indicate that family history is of significance.

Implications/Analysis of Clinical History

Epidermolysis bullosa is a term that refers to a group of disorders characterized by blister formation after mechanical trauma. Unless the condition is very mild, symptoms would have occurred as an infant. As well, one would have expected a family history of blistering disease. Another consideration is pemphigus foliaceus (a benign form of pemphigus), an autoimmune disorder that is characterized by blisters; however, the most common age at onset is 60 years. In both of these disorders one would expect some family history of blistering. Drug-induced pemphigus would present in a similar fashion, but this patient has not taken any medication recently.

The importance of the clinical history needs to be stressed. Drug-induced hypersensitivity reactions and some infectious diseases can present in this fashion. Drugs can cause an autoimmune injury (antigens expressed at the border between the dermis and epidermis). These drug-induced reactions can be so severe that “skin sloughing” can occur, and patients need to be treated in a fashion analogous to a burn victim. There are also inherited autoimmune diseases that can look like this (e.g., bullous pemphigoid—a disease caused by autoantibodies against the epidermis). A variety of infections result in blistering before blister breakage and healing (e.g., chickenpox, molluscum contagiosum).

None of these really fits this clinical presentation in general because the clinical history is suggestive of something recent, causing an acute change.

Implications/Analysis of Laboratory Investigation

Laboratory investigations were not necessary to determine therapy.

DIAGNOSIS

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