Internal Medicine

0521779407-17 CUNY1086/Karliner 0 521 77940 7 June 13, 2007 7:57

Photosensitivity 1173

Signs & Symptoms

■Phototoxicity is manifest by erythema in a photodistribution

■Photoallergy is manifest by an eczematous eruption in a photodis-

tribution

■Polymorphous light eruption – most often erythematous papules or

plaques without epidermal change

■Lupus erythematosus may be manifest as discoid lesions, or non-

scarring lesions (see Cutaneous LE chapter)

■PCT and pseudoporphyria are manifest as blisters, erosions, scars

and milia most commonly on the dorsal hands. Patients with PCT

may have hyperpigmentation and/or hypertrichosis

tests

■Basic blood tests:

➣ANA, Anti Ro (SS-A), anti-nDNA in patients with PMLE or possible

LE

➣None in patients with phototoxicity and photoallergy

■Basic urine tests:

➣Urinary porphyrins in patients with fragility or blisters of the

dorsal hands

■Specific diagnostic tests –

➣Hepatitis C antibody in patients diagnosed with PCT

➣Skin biopsy is helpful for diagnosis of LE

differential diagnosis

■PMLE and LE may be at times difficult to distinguish. LE often has

antibodies and the skin biopsy may help.

■PCT and pseudoporphyria can be differentiated by hypertrichosis

that occurs with PCT, both must be differentiated from epider-

molysis bullosa acquisita – immunofluorescence microscopy is

useful

management

What to Do First

■Establish the possibility that sunlight is involved with the condition

■Determine the pattern of the disease – phototoxicity vs. allergy vs.

endogenous disease vs. photoaggravated disease

■Determine the action spectrum – the wavelength of light that causes

or aggravates the disease. Phototesting may be helpful in reproduc-

ing the disease.

■Consider skin biopsy and other diagnostic tests