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

Workup for Increased Sun Sensitivity

A comprehensive workup for increased sun sensitivity should include detailed history, medication review, phototesting, and specific laboratory tests to identify the underlying cause, with referral to dermatology for specialized evaluation.

Initial Assessment

• Obtain a detailed history focusing on:

  • Timing and pattern of reactions (immediate vs delayed onset) 1, 2
  • Specific triggers (wavelength sensitivity - UVA, UVB, visible light) 1, 3
  • Distribution of affected areas (sun-exposed vs covered areas) 2, 4
  • Associated symptoms (burning, itching, rash characteristics) 3
  • Family history of photosensitivity disorders 1, 5

• Medication review is essential as many drugs can cause photosensitivity:

  • Antibiotics (especially tetracyclines, fluoroquinolones, sulfonamides) 6, 4
  • Cardiovascular medications (amiodarone, thiazide diuretics) 1, 7
  • Antidepressants (citalopram, escitalopram, fluoxetine) 1
  • NSAIDs (both topical and systemic) 4
  • Antihypertensives (ACE inhibitors, ARBs) 1

Physical Examination

• Document distribution and morphology of lesions:
  • Sun-exposed areas (face, neck, arms, hands) vs covered areas 2, 4
  • Presence of erythema, edema, vesicles, bullae, or scaling 3
  • Signs of chronic photodamage (poikiloderma, hyperpigmentation) 1
  • Ocular involvement (photophobia, conjunctival injection) 1

Laboratory Testing

• Basic laboratory studies:

  • Complete blood count with differential 1
  • Comprehensive metabolic panel 1
  • Antinuclear antibody (ANA) to screen for lupus erythematosus 2
  • Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) 2

• Specialized testing:

  • Porphyrin studies (urine, stool, and blood) to rule out porphyrias 2
  • Genetic testing for suspected xeroderma pigmentosum or other inherited photosensitivity disorders 1

Phototesting

• Phototesting should be performed by dermatology specialists:
  • Minimal erythema dose (MED) determination for UVA and UVB 1
  • Minimum urticarial dose (MUD) testing for suspected solar urticaria 1
  • Photopatch testing for suspected photoallergic contact dermatitis 4
  • Provocative testing with suspected wavelengths 1, 8

Skin Biopsy

• Consider skin biopsy of affected areas when:
  • Diagnosis remains unclear after initial evaluation 2
  • Suspicion for lupus erythematosus or other autoimmune conditions 2
  • Need to differentiate between photoallergic and phototoxic reactions 4

Special Considerations

• For suspected xeroderma pigmentosum:

  • Early referral to dermatology for specialized testing 1
  • Comprehensive skin examination for malignancies 1
  • Ophthalmologic and neurologic evaluations 1

• For suspected drug-induced photosensitivity:

  • Consider drug withdrawal and rechallenge under medical supervision 6, 3
  • Document timing between drug initiation and symptom onset 4

Management Approach

• Immediate measures:

  • Discontinuation of suspected photosensitizing medications when possible 6, 4
  • Sun protection with broad-spectrum sunscreens (SPF 30+) 1
  • Protective clothing, hats, and UV-resistant films on windows 1
  • Use of UV meters to assess environmental UV levels 1

• Referrals:

  • Dermatology for specialized phototesting and management 1
  • Ophthalmology for ocular manifestations 1
  • Genetics for suspected inherited disorders 1

Common Pitfalls to Avoid

• Failing to consider indoor light sources as potential triggers (fluorescent lighting can emit UVA) 8
• Overlooking drug-induced photosensitivity, which can persist for weeks to months after drug discontinuation 6, 3
• Not distinguishing between photoallergic (immune-mediated) and phototoxic (direct cellular damage) reactions, which require different management approaches 3, 4
• Missing rare but serious conditions like xeroderma pigmentosum, which requires aggressive photoprotection and cancer surveillance 1