Page 170 - The Netter Collection of Medical Illustrations - Integumentary System_ Volume 4 ( PDFDrive )

Plate 5-7 Integumentary System

LINEAR IMMUNOGLOBULIN A
BULLOUS DERMATOSIS

Linear immunoglobulin A (IgA) bullous dermatosis is
an infrequently encountered autoimmune blistering
disease that was originally described in 1979. This
disease has a characteristic immunofluorescence stain-
ing pattern that is used to differentiate it from other
blistering diseases such as dermatitis herpetiformis. As
the name implies, linear IgA is deposited along the
length of the dermal-epidermal junction. Chronic
bullous disease of childhood is considered by most to
be the same disease, although there are a few clinical
differences in age at onset and associations that can be
used to justify separating them into two distinct, albeit
very similar, entities. Most cases of chronic bullous der-
matosis of childhood are idiopathic, whereas most cases
of linear IgA bullous dermatosis are drug induced and
occur in an older population.
Clinical Findings: Linear IgA bullous dermatosis is
rare and is estimated to occur in 1 of every 2,000,000
people. There is no race or sex predilection. It occurs
most frequently in the adult population. The blistering
disease has an insidious onset with small vesicles that
may mimic dermatitis herpetiformis. The blisters are
pruritic and do not have the same burning sensation as
occurs in dermatitis herpetiformis, nor is there any rela-
tionship to dietary intake. The bullae in linear IgA
bullous dermatosis are characteristically arranged in a
“string of sausages” configuration. Each bulla is elon-
gated and tapers to an end, with a small area of inter-
vening normal-appearing skin before the tapering
beginning of a new bulla. This string can be linear or
annular in orientation. The blisters are tense and even-
tually rupture and heal with minimal scarring. Mucous
membrane involvement is frequently seen and can
resemble that of mucous membrane pemphigoid.
Chronic bullous disease of childhood manifests in
early childhood (4-5 years of age). The blistering is
similar to that of linear Ig bullous dermatitis, and the
histological findings are identical. Blistering in chronic
bullous disease of childhood is more often localized to
the abdomen and lower extremities but may occur any- Characteristic bullae of linear
where on the skin; it also commonly affects mucous IgA disease, or chronic bullous
membranes. Chronic bullous disease of childhood is disease of childhood. They are
most often idiopathic, whereas linear IgA bullous der- configured in an annular manner
matosis can also be seen in association with underlying with small areas of intervening
medications, malignancies, or other autoimmune con- normal skin.
ditions. Many medications have been implicated in
causing linear IgA bullous dermatosis, with vancomycin
being the most common by far.
Histology: The immunofluorescence staining pattern
is characteristic and shows linear IgA all along the base-
ment membrane zone. This is highly specific and sensi-
tive for the diagnosis of linear IgA bullous dermatosis
and chronic bullous disease of childhood. Routine hema-
toxylin and eosin staining shows a subepidermal blister
with an underlying neutrophilic infiltrate. This can be Linear deposition of IgA along the basement membrane zone
impossible to distinguish from dermatitis herpetiformis
or bullous lupus, so immunostaining is required.
Pathogenesis: The exact target antigen in linear IgA various mechanisms, ultimately leading to disruption of are best treated by recognizing the common culprits
bullous dermatosis is unknown. It is speculated that the the dermal-epidermal junction and blistering. and removing them immediately. Over a period of a few
IgA antibodies are directed against a small region of Treatment: The first line of therapy is dapsone. weeks, most patients who have discontinued the offend-
bullous pemphigoid antigen 180 (BP180). Other pos- Patients respond quickly to this medication. Low doses ing medication return to a normal state. If the disease
sible antigens exist and have been localized to the of dapsone are usually all that is needed. Alternative is found to be associated with an underlying malignancy
lamina lucida and lamina densa regions of the basement substitutes for dapsone include sulfapyridine and col- or other autoimmune condition, therapy with dapsone
membrane. The reason for formation of these anti- chicine. Oral prednisone can be helpful initially, but is warranted. Treatment of the underlying condition
bodies and how certain medications induce them are because of the long-term side effects, patients should should also be undertaken. If the malignancy or the
unknown. Once present, the antibodies target the be transitioned to one of the other medications men- associated disease is put into remission, there is a good
basement membrane zone and cause inflammation by tioned. Drug-induced variants of this blistering disease possibility that the blistering disease will remit as well.

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