What is the workup for a patient with increased sun sensitivity?

Workup for Increased Sun Sensitivity

A thorough workup for increased sun sensitivity should include a detailed history, physical examination, laboratory testing, and phototesting to identify the underlying cause and guide appropriate management.

Initial Assessment

• A comprehensive history should focus on timing and pattern of reactions, specific triggers, distribution of affected areas, associated symptoms, and family history of photosensitivity disorders 1
• Medication review is crucial as many drugs can cause photosensitivity, including:
  • Antibiotics (especially tetracyclines) 2, 3
  • Cardiovascular medications 1, 4
  • Antidepressants and other psychotropic drugs 3, 4
  • Nonsteroidal anti-inflammatory drugs 3, 4
  • Antihyperlipidemic agents 3
  • Antineoplastic drugs 3

Physical Examination

• Document the distribution and morphology of lesions, including signs of chronic photodamage 1
• Evaluate for ocular involvement such as photophobia and conjunctival injection 1
• Assess for specific patterns that might suggest particular photosensitivity disorders:
  • Erythema, swelling, blisters, exudation, peeling, burning, itching, or hyperpigmentation of sun-exposed areas 3
  • Distribution limited to sun-exposed areas versus generalized involvement 1

Laboratory Testing

• Basic laboratory studies should include:
  • Complete blood count with differential 1
  • Comprehensive metabolic panel 1
• Additional testing based on clinical suspicion:
  • Antinuclear antibody (ANA) testing for suspected lupus erythematosus 1
  • Porphyrin levels in urine, stool, and blood for suspected porphyrias 1
  • Genetic testing for suspected xeroderma pigmentosum or other inherited photosensitivity disorders 1

Phototesting

• Phototesting should be performed by dermatology specialists to determine:
  • Minimal erythema dose determination for UVA and UVB 1
  • Minimum urticarial dose testing for suspected solar urticaria 1
  • Photopatch testing for suspected photoallergic contact dermatitis 4

Differential Diagnosis

• Phototoxic reactions: occur in anyone given sufficient drug dose and UV exposure 4
• Photoallergic reactions: immune-mediated and require prior sensitization 4
• Polymorphic light eruption: affects 10-20% of the population in the northern hemisphere 5
• Lupus erythematosus: characterized by photosensitivity and systemic symptoms 1
• Porphyrias: group of metabolic disorders affecting heme biosynthesis 1
• Solar urticaria: rapid onset of urticaria after sun exposure 6, 1
• Chronic actinic dermatitis: persistent eczematous reaction in sun-exposed areas 6

Management Approach

• Immediate measures:

  • Discontinuation of suspected photosensitizing medications when possible 1, 3
  • Sun protection with broad-spectrum sunscreens (SPF ≥30 that is labeled as broad spectrum) 6, 7
  • Protective clothing, including broad-brimmed hats, long-sleeved shirts, and long pants 6
  • Avoidance of peak sun hours (10 AM to 4 PM) 6
  • Avoidance of sunlamps and tanning beds 6

• For patients with medication-induced photosensitivity:

  • Consider alternative medications with lower photosensitizing potential (e.g., cephalexin instead of tetracyclines) 2
  • If photosensitizing medication must be continued, advise taking it in the evening to minimize sun exposure risk 2

• Referrals:

  • Dermatology for specialized management and evaluation 1
  • Ophthalmology if ocular symptoms are present 1
  • Genetics for suspected inherited photosensitivity disorders 1

Patient Education

• Educate patients about the long-term risks of sun exposure, including premature aging, actinic keratoses, and skin cancers 8
• Emphasize the importance of using broad-spectrum sunscreens that protect against both UVA and UVB, as UVA can contribute significantly to photosensitivity reactions 7
• Advise regular skin self-examination and annual skin examinations by a dermatologist, especially for patients with chronic photosensitivity 6