Case 4 -
Chronic Actinic Dermatitis
Steven R. Tahan
Beth Israel Deaconess Medical Center
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22 year old male with a several month history of pruritic erythematous scaly plaques initially on the
posterior and sides of neck that spread to the anterior neck, upper chest, and later face, upper trunk,
and arms. Lesions are well demarcated and sharply cut-off at the collar. The eruption worsened in
Case 4 - Slide 1
Histology and Molecular Work-up
H&E sections show a predominantly spongiotic dermatitis combined with lymphocyte tagging along the
dermo-epidermal interface, focal lymphocyte exocytosis, focal papillary dermal fibrosis, and superficial
to deep dermal perivascular lympho-histiocytic infiltrate. Some lymphocytes have irregular nuclear
contours. Immunohistochemical stains reveal a predominantly T-cell (CD3+) infiltrate with CD4+:CD8:
ratio of approximately 1:1. No significant loss of CD5 and CD7 expression by the T-cells is appreciated.
DNA was amplified from paraffin sections, and no clonal rearrangement of the T-cell gamma receptor was
Differential and Final Diagnosis
The presentation of a cutaneous eruption beginning in light-exposed areas characterizes this disorder
in the group of a photo-aggravated dermatoses. This broad spectrum of disorders that includes
polymorphous light eruption, auto-immune connective tissue diseases, porphyrias, DNA repair defects
(xeroderma pigmentosum), solar urticaria, contact photo-allergic dermatitis, and drug induced
photo-allergic dermatitis, and chronic actinic dermatitis/actinic reticuloid (etiology unknown).
The histologic picture combines spongiosis with prominent lymphocyte tagging along the dermo-epidermal
junction, patchy papillary dermal fibrosis, and a superficial perivascular lymphocytic infiltrate.
Polymorphous light eruption, in contrast, is typically markedly edema, particularly in early phases, and
lacks features of chronicity. Cutaneous manifestation of auto-immune connective tissue diseases exhibit
more significant vacuolar interface degeneration with apoptosis, cytoid body formation, follicular
keratin plugging, thickening of the basement membrane zone, deep perifolliculitis, and increased dermal
mucins. Porphyrias are characterized by hyaline thickening of vessel walls and the basement membrane
zone, often with subepidermal bulla. Eruptions of xeroderma pigmentosum show a mild non-specific
perivascular lymphocytic infiltrate, telangiectasias, and prominent melanin pigmentation along basal
layers of the epidermis with foci of hypomelanization. Solar urticaria is pauci-inflammatory with edema.
Photo-allergic dermatitis, either in response to a contactant or systemic trigger, usually includes
eosinophils among the inflammatory infiltrate. Chronic actinic dermatitis is an idiopathic reaction
triggered by light, and best fits the pathologic changes combining eczematous features and lymphocytic
infiltrate. The presence of lymphocyte tagging along the dermo-epidermal junction, foci of lymphocyte
epidermotropism, cellular enlargement, sometime with nuclear infoldings, papillary dermal fibrosis, and
chroncity raise some concern for a T-cell dyscrasia/evolving mycosis fungoides . The CD4:CD8 ratio of 1:1
with retention of CD5 and CD7 expression, and absence of a clonal T-cell gamma receptor rarrangement,
however, argue against mycosis fungoides. Despite the somewhat early age of onset in this individual,
the final diagnosis is chronic actinic dermatitis ("actinic
Historical Recognition of Chronic Actinic Dermatitis
Chronic actinic dermatitis (CAD, synonyms, photosensitivity dermatitis,
persistent light reaction, actinic reticuloid, photosensitive eczema) is a persistent, often
chronic eczematous eruption triggered by exposure to light . It was first described by
Haxthausen in 1933 in a patient who developed a persistent hypersensitivity reaction to light following
intravenous injection of trypaflavine. In the 1960s similar reactions were described with other drugs
and following contact to household substances
In 1969 the condition was reported in a
severe form with widespread cutaneous involvement and designated "actinic reticuloid" . This
was followed by reports of milder forms under the appellations "photosensitive eczema" and
"photosensitivity dermatitis" . In 1979 this spectrum of disorders was grouped under the
umbrella name "chronic actinic dermatitis" .
CAD occurs in worldwide distribution and affects individuals of all skin colors. It is most common
among older men living in temperate climates. No familial tendency has been recognized. It may develop
in normal skin or in patients with a history of endogenous eczema, photoallergic or allergic contact
dermatitis, and unusually oral drug hypersensitivity, or polymorphous light eruption (see below). Some
patients have allergic contact sensitivity to airborne allergens including plant antigens, fragrances, or
The eruption is characterized by an eczematous pruritic eruption on light exposed areas such as the
scalp, face, back and sides of neck, upper chest, dorsal aspects of arms and hands. A past history of
atopy, allergic contact dermatitis, seborrheic dermatitis, or polymorphous light eruption, is not
Commonly there is a sharp cut-off at lines of clothing and sparing of upper
eyelids, skin beneath earlobes, web spaces, and other sun-protected areas. Lesions are pruritic and can
be patchy or confluent, papular or plaque-like, often with lichenification. Ezcema of the palms and
soles may develop. In some individuals lesions may spread to covered areas and even lead to
erythroderma. Severely affected individuals can experience pruritus, lymphadenopathy, atypical
lymphocytes in peripheral blood, alopecia, palmarplantar hyperkeratosis, and onychodystrophy. These
cases can bear close resemblance to Sezary syndrome. Malignant transformation has been claimed, but not
convincingly demonstrated. Rare cases of erythrodermic cutaneous T cell lymphoma have been reported to
exhibit photosensitivity .
CAD exhibits variable pathology ranging from interface dermatitis to florid spongiotic dermatitis with
psoriasiform epidermal hyperplasia, atrophy, or combinations of these .
Characteristically there is a moderately dense perivascular and interstitial dermal infiltrate of
medium-sized lymphocytes, often with foci of epidermotropism or tagging along the dermal-epidermal
junction. Some lymphocytes can have convoluted and even cerebriform nuclei. These cells are often
epidermotropic and may form Pautrier-like microabscesses, resembling mycosis fungoides. The presence of
eosinophils in the infiltrate can raise consideration for, but is not diagnostic of, a drug or topical
Chronic older lesions have variable, often marked acanthosis, variable scaling, and papillary dermal
fibrosis. Sometimes Pautrier's-like lymphocyte collections develop within the epidermis. In the
papillary dermis vertically streaked fibrosis, occasional stellate fibroblasts, and small multinulcleated
cells, sometimes referred to as Montgomery giant cells are present. In the deeper dermis there can be
dense perivascular aggregates of predominantly T-cells with admixed histiocytes, eosinophils, and
sometimes plasma cells. In severe CAD, there may be prominent, albeit focal, lymphocyte exocytosis with
some cells exhibiting irregular nuclear contours. The predominance of CD8+ phenotype and absence of
clonal T-cell gamma receptor rearrangements (see below) is helpful in distinguishing these cases from
mycosis fungoides (MF).
Immunophenotyping of infiltrating T cells can be very helpful in distinguishing CAD/actinic reticuloid
from mycosis fundgoides . In CAD, the CD4 subpopulation of T cells is nearly equal or less
than the CD8 population in contrast toCTCL where in most cases, CD4 cells out number CD8 cells by nearly
10 fold (except for the uncommon cases of CD8+ mycosis fungoides). This difference is accentuated in
peripheral blood samples where CD4/CD8+ ratio was in a recent study found to range from 0.3 – 1.6 in
CAD/actinic reticuloid compared to a range of 0.9 – 92 in Sezary syndrome.
Molecular studies using PCR in combination with denaturing gradient gel electrophoresis for assessment
of clonal T cell receptor gamma gene rearrangements have consistently shown an absence of clonal
rearrangements in actinic reticuloid
The pathogenesis of CAD is not well understood. The clinical features, nature and pattern of dermal
inflammatory infiltrate, cytokine production, and adhesion molecule activation are all very similar to
those of allergic contact dermatitis. This is a delayed-time hypersensitivity response, and it appears
that the CAD represents a reaction to a photo-activated endogenous cutaneous autoantigen
Some studies have suggested that the ultraviolet radiation absorber may be DNA or an
associated molecule .
CAD is diagnosed by means of a combination of clinical findings, abnormal response of clinically
normal skin to exposure to light irradiation, and supporting histologic findings. Inducing wavelengths
are in the UVB range in most patients, but for some in the UVA and visible light spectrums. Anti-nuclear
anti-Ro and anti-La antibody titers are normal, as are blood, urine, and stool porphyrin concentrations.
In drug and chemical photosensitivity, history of exposure to an inducing substance supported by positive
patch testing is required. Mycosis fungoides is usually not, but may occasionally be mildly
photosensitive. Of note, Sezary-like cells can be found in circulating blood in erythrodermic CAD, but a
low CD4:CD8 ratio and absence of T-cell clonality will help to steer the diagnosis away from MF.
- Actinic reticuloid
- Chronic actinic dermatitis
- Persistent light reaction
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