Photodermatology & Porphyrias Flashcards
What is photobiology?
Study of non-ionising radiation on living systems
What is cutaneous photosensitivity and what are the 2 types?
-abnormal cutaneous response to UV radiation (light) -phototoxicity & photoallergy
Roughly outline reaction to sun based on Fitzpatrick sun-reactive skin phototypes: SPT I - SPT VI?
SPT I - can’t tan always burns SPT II/III: burns then tans (approximate) SPT IV: never burns
Examples of non-ionising radiation?
-visible light -near UV light -infrared -microwave -radio waves
Which site involvement is a clue to cutaneous photosensitivity? (eyelids, dorsal distal fingers, retroauricular, sub-mental?)
retroauricular
porphyrins as chromophores
chemicals that absorb radiation
What are porphyrias and what body systems/organs can they affect?
Group of disorders associated with the liver that lead to build up of porphyrins in the body -affect skin and nervous system
What are porphyrins the main precursor of?
Heme
What is basic pathophysiology behind porphyrias?
deficiency in enzymes that convert porphyria to other substances which leads to build up in porphyrins
Porphyria cutanea tarda enxyme + hepatic/erythropoetic?
-uroporphyrinogen decarboxylase -hepatic e.g. genetic haemochromatosis
What are 4 main groups of porphyrias?
-phototoxic skin e.g. erythropoietic protoporphyria -blistering and fragility skin porphyrias -acute attack -severe congenital porphyrias e.g. congenital erythropoetic porphyria
Which is most common and how does it present?
porphyria cutanea tarda -blisters and fragility of skin in sunlight
How do calcium deposits present?
hard
What are these and why not bullae and why not calcium deposits?
milia -too firm to be bullae -too soft to be calcium deposits
unilocular vs multilocular?
unilocular single blister -multilocular-> more often superficial, different levels
How can PCT also present? ( 6 ways)
-blisters -fragility -hyperpigmentation -hypertrichosis -solar urticaria -morphea
What is hypertrichosis?
excess hair growth
Morphea?
painless skin discolouration
woods lamp use?
diagnostic test that can detect bacteria;, fungal infections or skin pigment disorders
What are 4 underlying causes of PCT?
-alcohol -viral hepatitis -oestrogens -haemochromatosis
What is aim of treatment in PCT? (2)
-relieve skin disease -treat underlying diseases
What enzyme has reduced activity in erythropoietic protoporphyria causing a build up of protoporphyrin?
ferrochelatase
How does erythropoietic protopophyria present?
-severe pain on sun exposure -subtle swelling -linear lines scars
investigations for erythropoietic protoporphyria?
-measure red blood cell porphyrins -fluorocytes -transaminases -red cell indices as often anaemic (dont give iron cos can end up feeding pathway that lacks enzymes)
