DERMATITIS HERPETIFORMIS
Dermatitis herpetiformis is a unique chronic blistering disease that can be seen in isolation or in conjunction with celiac sprue. Dermatitis herpetiformis is the cutaneous manifestation of underlying gluten sensitivity. Patients with a genetic predisposition seem to be at risk for development of immunoglobulin A (IgA) autoantibodies that cross-react with gluten proteins and specific components of the skin and gastrointestinal tract. Dermatitis herpetiformis is always associated with small-bowel disease, and in some cases celiac sprue coexists. Patients with dermatitis herpetiformis are at increased risk for development of lymphoma of the gastrointestinal tract, potentially caused by the chronic inflammation and stimulation of the gastrointestinal-associated lymphatic tissue. Following a gluten-free diet cures the disease in both the skin and gastrointestinal locations.
Clinical
Findings: Dermatitis herpetiformis is most frequently seen in the
fourth and fifth decades of life, with a higher prevalence in the female
Caucasian population. The reason for this preference may be that dermatitis
herpetiformis has associations with the human leukocyte antigen (HLA) DQ2 and
DQ8 haplotypes. Dermatitis herpetiformis manifests as a symmetric vesicular
eruption, which is often preceded by a burning sensation or pruritus. The
extensor surfaces of the elbows, knees, and lower back, as well as the scalp,
may be involved. The vesicles are fragile and break easily. Erosions and
excoriations are frequently seen. Diarrhea can be a recurrent complaint,
secondary to involvement of the small bowel. Patients frequently report a flare
of the rash and abdominal pain and diarrhea after eating certain foods.
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| CELIAC SPRUE AND DERMATITIS HERPETIFORMIS |
Laboratory
testing is frequently performed. High levels of IgA anti–tissue
transglutaminase (anti-tTG) antibody and antiendomysial antibodies (EMAs) are
commonly found and are highly specific for dermatitis herpetiformis. In cases
of suspected sprue, an upper endoscopy can be performed, with a biopsy of the
small bowel to evaluate for the characteristic villous atrophy. Pathogenesis:
Dermatitis herpetiformis is an auto immune blistering disease that is
caused by the development of specific antibodies, notably anti-tTG and EMAs.
Tissue transglutaminase (tTG) is very similar to epidermal transglutaminase,
and it is believed that the anti-tTG antibodies attack both proteins. This
disruption of the epidermal transglutaminase is thought to be responsible for
the blistering skin findings. Once the antibodies attach to the epidermal
transglutaminase protein, the complement cascade and various cytotoxic cellular
events are activated. The anti-EMA test is the most specific of the antibody
tests for dermatitis herpetiformis.
Histology:
Early
lesions of dermatitis herpetiformis show subepidermal clefting with a
neutrophil-rich infiltrate in the papillary dermis. As the lesions progress,
subepidermal blistering becomes prominent, and the papillary dermis is filled
with neutrophils. The histological findings of dermatitis herpetiformis can be
difficult to differentiate from those of linear IgA bullous dermatosis on
routine hematoxylin and eosin staining. Direct immunofluorescence is required
to differentiate the two diseases. The direct immunofluorescence staining
pattern in dermatitis herpetiformis is that of a speck-led arrangement of IgA
within the papillary dermis. In linear IgA bullous disease, as the name
implies, a linear pattern along the basement membrane zone is seen.
Treatment:
The
treatment of dermatitis herpetiformis is twofold. The first aspect of therapy
is to control the itching and blistering.
This can be rapidly achieved with dapsone or sulfapyridine. The response to
these two medications is remarkably quick, with most patients noticing
near-resolution of their symptoms within 1 day. In cases of suspected
dermatitis herpetiformis that has not been confirmed histologically, dapsone
can be used as a therapeutic test: If the patient sees a rapid response after
the first day of dapsone therapy, the diagnosis is most certainly dermatitis
herpetiformis. Dapsone or alternative medications can treat the blistering and
pruritus, but they do not decrease the long-term risk of small-bowel lymphoma.
The only means of decreasing and removing the risk of lymphoma is to have the
patient adhere to a strict gluten-free diet. This requires nutritional education.
If patients are able to entirely avoid gluten-containing products, not only
will the rash resolve, but the gastrointestinal abnormalities will resolve, and
the risk of lymphoma will return to that of the generalb population.
