Photosensitive Disorders

Key Terms

Polymorphous Light Eruption

Polymorphic light eruption

Systemic Lupus Erythematosus

Bullous systemic lupus erythematosus

Discoid lupus erythematosus

Lupus hair

Discoid Lupus Erythematosus

Chronic cutaneous lupus erythematosus

Hypertrophic discoid lupus erythematosus


Amyopathic dermatomyositis

It is important to recognize photosensitive disorders because many of these conditions may be ameliorated, or prevented entirely, by sun avoidance and/or withdrawal of a photosensitizing medication. Also, this dermatologic pattern includes some forms of connective tissue disease that may have systemic consequences, including end-organ damage and even death.

Differential Diagnosis of Photosensitive Disorders

  • Actinic prurigo

  • Chronic actinic dermatitis

  • Dermatomyositis

  • Erythropoietic protoporphyria

  • Lupus erythematosus

  • Pellagra

  • Photoallergic contact dermatitis

  • Photoallergic drug eruptions

  • Phototoxic drug eruptions

  • Phototoxic contact dermatitis

  • Polymorphous light eruption

  • Porphyria cutanea tarda

  • Solar urticaria

  • Sunburn

Important History Questions

How long have you had a photoaggravated skin condition?

Some photosensitive disorders are acute, such as photoallergic contact dermatitis or photoinduced drug eruptions, whereas other conditions are chronic, such as erythropoietic protoporphyria or pellagra.

Do your lesions itch or burn?

Many photosensitive processes, such as actinic prurigo, chronic actinic dermatitis, and photoinduced drug eruptions, produce pruritus, whereas others may cause pain, such as erythropoietic protoporphyria, phototoxic drug eruptions, and sunburn.

Have you recently started any new medications?

This question is important when considering photoallergic and phototoxic drug eruptions. It could also be important when investigating drug-induced lupus erythematosus or drug-induced dermatomyositis.

Do you have any other symptoms or recent problems such as muscle pain, joint pain, fever, or other unexplained problems?

This question may reveal overt systemic symptoms, but more in-depth questioning and a complete review of symptoms may be necessary when connective tissue disorders, including lupus erythematosus and dermatomyositis, are specific considerations.

Is there a family history of a similar rash?

Some photodistributed conditions may have a hereditary component, such as actinic prurigo, erythropoietic protoporphyria, and polymorphous light eruption.

Important Physical Findings

Is there any evidence of hair loss?

Systemic lupus erythematosus may be associated with a nonscarring hair loss (so-called lupus hair); discoid lupus erythematosus may demonstrate a scarring alopecia, with characteristic dyspigmented plaques.

What is the distribution of the lesions?

Some disorders manifest a characteristic distribution. For example, systemic lupus erythematosus on the hands usually involves the interphalangeal skin (between joints), whereas dermatomyositis usually involves the skin over the joint spaces (as Gottron papules).

Is a mucosal surface involved?

Although most photosensitive disorders do not have mucosal involvement, discoid lupus, systemic lupus erythematosus, and actinic prurigo are notable exceptions, and all may have oral manifestations.

Does the patient have periungual telangiectasias?

Periungual telangiectasias may be seen in dermatomyositis and systemic lupus erythematosus.

Polymorphous Light Eruption

ICD10 code L56.4



Polymorphous light eruption (PMLE), also known as a polymorphic light eruption, is the most common photodermatosis, with some studies having shown an incidence that approaches 10% of the population in certain ethnic groups. Familial clustering and a higher incidence in some ethnic groups suggest a genetic predisposition, although the precise pathogenesis is not well understood. It is thought that PMLE represents a form of a delayed-type hypersensitivity process (type IV). PMLE may be precipitated by ultraviolet A (UVA) light (most common), UVB light ( Fig. 19.1 ), or both, depending on the patient.

Fig. 19.1

Phototest with red plaques being produced in as little as 2 seconds of UVB exposure.

Clinical Features

  • PMLE is more common in women, and it generally presents in the first 3 decades of life.

  • Patients with PMLE usually develop a photoexposed eruption in the early spring, with fewer lesions later in the summer (due to hardening) or in the fall, when the UV light intensity wanes.

  • The threshold of exposure necessary for the development of lesions may vary from 5 minutes to 3 hours.

  • The delay between UV light exposure to the development of lesions is highly variable (30 minutes to 3 days).

  • The morphology of PMLE varies widely (hence the term polymorphous) and includes macular erythema ( Fig. 19.2 ), erythematous papules and plaques ( Figs. 19.3 and 19.4 ), and papulovesicles with a dermatitic appearance ( Fig. 19.5 ). In some cases, the lesions may resemble urticaria or erythema multiforme.

    Fig. 19.2

    Young lady with macular erythema of the cheeks, nose, and chin that resemble the malar rash of systemic lupus erythematosus.

    (From the William Weston Collection, Aurora, CO.)

    Fig. 19.3

    Young child with red indurated plaques confined to the sun-exposed portions of the arm.

    (From the William Weston Collection, Aurora, CO.)

    Fig. 19.4

    Polymorphous light eruption presenting as plaques of the cheek in a young man.

    (From the Fitzsimons Army Medical Center Collection, Aurora, CO.)

    Fig. 19.5

    Crusted dermatitic presentation of polymorphous light eruption in a child.

    (From the William Weston Collection, Aurora, CO.)

  • Pruritus is common.

Clinical Diagnosis

  • Clinical circumstances, including an affirmative family history, or appropriate ethnic background, may suggest the diagnosis.

  • A 3- or 4-mm punch biopsy may be supportive, but the histologic changes are not always diagnostic of only PMLE.

  • Screening laboratory studies to consider include antinuclear antibody (ANA) or extractable nuclear antigen antibody (ENA) testing and determination of urine or stool porphyrin levels to exclude porphyria.

  • Rare cases may require phototesting (see Fig. 19.1 ).


  • Artificial light exposure can be used to harden an individual and decrease observed disease. Narrow-band UVB (NB-UVB) is the preferred modality, followed by PUVA (psoralen plus UVA). Broadband UVB is less effective.

  • Oral hydroxychloroquine (200–400 mg qd) is effective for many patients.

  • Oral β-carotene (25–50 mg tid) is effective for some patients.

  • Oral nicotinamide (1 g tid) induced complete remission in 14 of 25 patients and improved the course of disease in the remaining 11 patients.

  • Topical corticosteroids may be helpful, with the strength of the corticosteroid varied according to the amount of disease that is present and the skin affected.

  • Sun avoidance behaviors, sun-blocking clothing, and broad-spectrum sunscreens (with UVA and UVB protection) are important strategies to minimize disease activity.

Clinical Course

Lesions of PMLE typically last for 1 to 3 weeks and heal without scarring. The disorder may persist for decades, but the condition usually remits later in life.

Photoallergic Drug Eruption

ICD10 code L56.1


Commonly Implicated Drugs in Photoallergic Drug Eruptions

  • Celecoxib

  • Dapsone

  • Furosemide

  • Hydrochlorothiazide (very common)

  • Hydroxychloroquine

  • Pyridoxine hydrochloride (vitamin B 6 )

  • Trimethoprim-sulfamethoxazole (TMP-SMX)

  • St. John’s wort


Photoallergic drug eruptions are eczematoid tissue reactions that occur after the ingestion of a medication, vitamin, supplement, or even a preservative in food, but the condition requires light exposure for the reaction to transpire. Photoallergic drug reactions can be induced by UVA (most common) or UVB light. Many texts have combined photoallergic and phototoxic drug eruptions into one category of photosensitive drug eruptions, but the processes are distinct, and a separate discussion is warranted.

Clinical Features

  • With prior sensitization, photoallergic reactions usually occur 1 day after re-exposure. A new exposure may take up to 3 weeks to foment as a photoallergy.

  • The condition causes a photodistributed dermatitis that usually involves the face, posterior neck, upper chest, arms, and hands. There is usually sparing beneath the chin, in a natural shadow area.

  • The condition can spread somewhat to non–sun-exposed areas as UV light penetrates clothing.

  • Primary lesions vary from macular erythema to indurated eczematous plaques or even, on occasion, vesiculobullous reactions ( Figs. 19.6–19.8 ).

    Fig. 19.6

    Patient with photoallergic dermatitis manifesting as pruritic erythema on the forehead, malar cheeks, and chin due to cotrimoxazole.

    (From the Fitzsimons Army Medical Center Collection, Aurora, CO.)

    Fig. 19.7

    Patient with photoallergic erythema and induration of the malar cheeks and V of the neck caused by hydrochlorothiazide, one of the most common causes of photoallergic drug eruptions.

    Fig. 19.8

    Patient with eczematoid photoallergic erythema of the ears, lateral neck, and V of the neck caused by prochlorperazine, which is a relatively uncommon cause of photoallergy.

  • In contrast to phototoxic drug eruptions, which produce discomfort or pain similar to that of a sunburn, photoallergic drug eruptions are usually pruritic.

Clinical Diagnosis

  • A pruritic dermatitis, in a photodistributed or photoaccentuated pattern, and occurring in a patient taking medication(s) or a suspicious exogenous agents, raises concern for a photoallergic drug eruption.

  • In some cases, it is difficult to distinguish a photoallergic drug eruption from a contact dermatitis to pollen or sunscreen, which tend to occur on photoexposed portions of the skin.

  • Biopsies demonstrate nonspecific features of dermatitis but are only useful in excluding some photosensitive conditions, such as lupus erythematosus, dermatomyositis, or phototoxic drug eruption.

  • In many cases, the diagnosis is only definitively established after removal of the suspected exogenous agent, with observed clinical improvement.


  • Withdrawal of the suspected exogenous agent is a critical element of management.

  • Sunlight and allergen avoidance are important to management. Patients should understand that UVA wavelengths, which produce most drug-induced photoallergic drug eruptions, can pass through window glass and produce disease.

  • Use of moderate to potent topical corticosteroids is an effective topical treatment.

  • Severe cases may require 3 to 14 days of oral prednisone (10–40 mg per day).

Clinical Course

Discontinuing the offending drug usually results in complete resolution in 2 to 3 weeks, although some reactions may persist for a longer duration.

Phototoxic Drug Eruption

ICD10 code L56.0


Commonly Implicated Drugs and Foods in Phototoxic Eruptions

  • Amiodarone

  • Capecitabine

  • Celery root

  • Demeclocycline

  • Doxycycline

  • 5-Fluorouracil

  • Flutamide

  • Methotrexate

  • Nonsteroidal antiinflammatory drugs (NSAIDs; weak phototoxic drugs)

  • Psoralen

  • Tetracycline

  • Voriconazole


Phototoxic drug eruptions are dose-related events. Because the reactions are not immunologically mediated, the condition will occur in any person given enough of the drug and incurring sufficient light exposure. In many cases, phototoxic drug eruptions resemble sunburn, but some drugs produce characteristic reactions, such as the onycholysis observed with tetracyclines or bullous reactions, which resemble porphyria cutaneous tarda caused by naproxen. Rarely, phototoxic eruptions are due to foods (e.g., celery root). Note that oral psoralen, in combination with UVA light (PUVA), is an intentional (iatrogenic) phototoxic drug eruption used to treat dermatologic disease.

Clinical Features

Sep 15, 2018 | Posted by in Dermatology | Comments Off on Photosensitive Disorders
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