Photodermatology & Porphyrias

Question 1

What is photobiology?

Answer 1

Study of non-ionising radiation on living systems

Question 2

What is cutaneous photosensitivity and what are the 2 types?

Answer 2

-abnormal cutaneous response to UV radiation (light) -phototoxicity & photoallergy

Question 3

Roughly outline reaction to sun based on Fitzpatrick sun-reactive skin phototypes: SPT I - SPT VI?

Answer 3

SPT I - can’t tan always burns SPT II/III: burns then tans (approximate) SPT IV: never burns

Question 4

Examples of non-ionising radiation?

Answer 4

-visible light -near UV light -infrared -microwave -radio waves

Question 5

Which site involvement is a clue to cutaneous photosensitivity? (eyelids, dorsal distal fingers, retroauricular, sub-mental?)

Answer 5

retroauricular

Question 6

porphyrins as chromophores

Answer 6

chemicals that absorb radiation

Question 7

What are porphyrias and what body systems/organs can they affect?

Answer 7

Group of disorders associated with the liver that lead to build up of porphyrins in the body -affect skin and nervous system

Question 8

What are porphyrins the main precursor of?

Answer 8

Heme

Question 9

What is basic pathophysiology behind porphyrias?

Answer 9

deficiency in enzymes that convert porphyria to other substances which leads to build up in porphyrins

Question 10

Porphyria cutanea tarda enxyme + hepatic/erythropoetic?

Answer 10

-uroporphyrinogen decarboxylase -hepatic e.g. genetic haemochromatosis

Question 11

What are 4 main groups of porphyrias?

Answer 11

-phototoxic skin e.g. erythropoietic protoporphyria -blistering and fragility skin porphyrias -acute attack -severe congenital porphyrias e.g. congenital erythropoetic porphyria

Question 12

Which is most common and how does it present?

Answer 12

porphyria cutanea tarda -blisters and fragility of skin in sunlight

Question 13

How do calcium deposits present?

Answer 13

hard

Question 14

What are these and why not bullae and why not calcium deposits?

Answer 14

milia -too firm to be bullae -too soft to be calcium deposits

Question 15

unilocular vs multilocular?

Answer 15

unilocular single blister -multilocular-> more often superficial, different levels

Question 16

How can PCT also present? ( 6 ways)

Answer 16

-blisters -fragility -hyperpigmentation -hypertrichosis -solar urticaria -morphea

Question 17

What is hypertrichosis?

Answer 17

excess hair growth

Question 18

Morphea?

Answer 18

painless skin discolouration

Question 19

woods lamp use?

Answer 19

diagnostic test that can detect bacteria;, fungal infections or skin pigment disorders

Question 20

What are 4 underlying causes of PCT?

Answer 20

-alcohol -viral hepatitis -oestrogens -haemochromatosis

Question 21

What is aim of treatment in PCT? (2)

Answer 21

-relieve skin disease -treat underlying diseases

Question 22

What enzyme has reduced activity in erythropoietic protoporphyria causing a build up of protoporphyrin?

Answer 22

ferrochelatase

Question 23

How does erythropoietic protopophyria present?

Answer 23

-severe pain on sun exposure -subtle swelling -linear lines scars

Question 24

investigations for erythropoietic protoporphyria?

Answer 24

-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)

Question 25

management of EPP

Answer 25

-genetic counselling -6 months LFTS and RBC porphyrins -visible light photoprotection measures

Question 26

What are 4 main photoprotection measures?

Answer 26

-behavioural -clothing -environmental -topical

Question 27

acute intermittent porphyria research this

Answer 27

consider differential guillain barre syndrome

Question 28

does acute intermittent porphyria usually affect the skin?

Answer 28

no