Investigation of the Photosensitive Child

Photosensivity disorders in childhood frequently can be diagnosed and managed in the general dermatology clinic. Occasionally, when diagnostic doubt exists, referral to a specialist unit is required for diagnostic phototesttng. Light testing equipment is fickle by nature, making such units uncommon. Phototesting using monochrometor or provocation systems takes approximately 45 minutes. Immediate and delayed readings over the following 48 hours as appropriate are required to cover the diagnostic possibilities. Individual diseases are characterized by particular patterns of wavelength dependency and evolution of the abnormal response. Other investigations that may be required are autoantibodies to exclude lupus erythematosus, a porphyrin scan leading to full studies and, on occasion, cell mutation or survival, and chromosome studies for the rarer genophotodermatoses. Good investigative data frequently help clarify the common clinical variants.