3 - photosensitivity & UV skin Flashcards
what is fitzpatrick skin classification?
I = only burns
II = burns, can tan
III = tans, can burn
IV = tans
V = dark brown skin
VI = black skin
what is polymorphic light eruption?
when get abnormal reaction to UV light, type IV hypersensitivity making papules & vesicles rash
= resolves in 1-2 weeks
what drugs are known for causing photosensitivity?
thiazide, chlorpromazine, doxycycline, quinine, amiodarone
what are 2 examples of conditions aggravated by sunlight?
SLE (lupus) or psoriasis
what is xeroderma pigmentosum?
= autosomal genetic disorder where deficiency in skin DNA repair which makes rapid photoageing & skin cancer in kids
- most die by teens or early adult from skin cancer (try to avoid sunlight)
what is porphyria?
= group of photosensitivity disorders from defect in enzyme needed in haem production (porphyrin ring is component of Hb and if Hb not made then porphyrin accumulates = problems)
what are 3 main types of porphyria (that i should know about it)?
- acute intermittent porphyria
- porphyria cutanea tarda
- erythropoietic protoporphyria
what is acute intermittent porphyria? presents?
type of porphyrin accumulation which often in 30yr females presenting with
- acute abdomen
- mood disturbance
- neurological
- seizures
what is porphyria cutanea tarda?
= most common type of porphyrin accumulation, in middle aged man - assoc w liver disease
how does porphyria cutanea tarda present?
- blistering lesions on sun exposed areas that heal with scarring & hyperpigmentation
- hypertrichosis
- solar urticaria
- morphea (thickening & hardening- fibrosis)
what investigation and management for porphyria cutanea tarda?
INVESTIGATION
- porphyrin studies
- woods lamp = urine pink not blue
TREATMENT
- treat underlying cause e.g. alcohol, viral hepatitis, oestrogens, haemochromatosis
what is erythropoietic protoporphyria? presents?
= porphyrin accumulation in children
presents w burning & itching of skin on exposure (might be no rash) = baby crying in sun
what is management of erythropoietic protoporphyria?
- light protection
- prophylactic TL-01 phototherapy
- antioxidants
- avoid iron
- treat liver failure if present
what enzyme deficiency & porphyrin type accumulated in each porphyria type? (idk if need to know)
a) acute intermittent porphyria
b) porphyria cutanea tarda
c) erythropoietic protoporphyria
a) porphobilinogen deaminase deficiency = porphobilinogen accumulates
b) uroporphyrinogen decarboxylase deficiency = uroporphyrinogen 3 accumulates
c) ferrochelatase deficiency = protoporphyrin IX accumulated
