Photosensitivity disorders Flashcards
What is a photosensitivity disorder?
An abnormal response to light or a normal response to abnormal levels of light.
Name three forms photosensitivity can take.
Xeroderma Pigmentosum, Drug phototoxicity and Porphyrias.
What is XP?
A decreased ability to repair DNA damage caused by UV light. Leads to cancer and cataracts.
What is drug phototoxicity?
When a drug reacts with light or sensitises the body to light.
Name three types of porphyria.
Erythropoietic protoporphyria (EPP) Porphyria Cutanea Tarda (PCT) Acute intermittent porphyria (AIP)
Porphyria Cutanea Tarda (PCT) is caused by loss of which enzyme?
Uroporphyrinogen decarboxylase (UD)
What chemical causes symptoms in Porphyria Cutanea Tarda (PCT)?
Uroprophyrinogen III which causes blistering at the dermo-epidermal junction.
How does Porphyria Cutanea Tarda (PCT) present?
BListering, skin fragility, hyperpigmentation, solar urticaria, scleroderma.
How do you treat Porphyria Cutanea Tarda (PCT)?
Diagnose and treat underlying cause.
Relieve skin symptoms.
What are some of the underlying causes of Porphyria Cutanea Tarda (PCT)?
Chronic liver disease (alcohol, hepatitis)
Oestrogens
Haemochromatosis
Loss of what enzyme is responsible for Erythropoietic protoporphyria (EPP)?
Ferrochelatase.
What chemical causes symptoms in Erythropoietic protoporphyria (EPP)?
Protoporphyrin IX
How does Erythropoietic protoporphyria (EPP) present?
Acute photosensitivity, usually, in childhood.
Pain, swelling, erythema, itch.
How do you manage Erythropoietic protoporphyria (EPP)?
Limit sun exposure.
Be careful with drugs as can make it worse due to liver problems.
