Introduction to Photodermatology and Porphyrias Flashcards
(41 cards)
What is photobiology defined as?
The study of non-ionising radiation on living systems
What does photobiology encompass?
Botany, zoology, medicine
What are photodermatoses?
Skin conditions with an abnormal reaction to light
Shorter wavelengths of light have more ______
ENERGY
Longer wavelengths of light have more __________
PENETRANCE
Why may sparing of the area of skin behind the ear lead you to suspect photosensitivity?
The area of skin behind the ear is not usually exposed ti sunlight/light
Why are there so many different porphyrias?
There is a huge range of enzymes in the pathway that converts glycine +succinyl CoA to Haem that can be missing or defective
What is a porphyria?
A rare hereditary disease in which there is abnormal metabolism of the blood pigment haemoglobin.
Porphyrins are excreted in the urine, which becomes dark; other symptoms include mental disturbances and extreme sensitivity of the skin to light
A group of uncommon diseases caused by something going wrong with the production of chemicals known as porphyrins
Porphyrias are due to abnormal metabolism of ___________
HAEMOGLOBIN
Outline the 4 main groups of porphyrias.
- Phototoxic
- Blistering and fragility
- Acute attack
- Severe congenital
Give an example of a phototoxic porphyria.
Erythropoietic protoporphyria
Give an example of a congenital porphyria.
Congenital erythropoetic porphyria
Describe what patients with a severe attack porphyria experience on exposure to light.
Prickly, burning pain on the exposed areas
What are the 3 most common skin porphyrias in Scotland? Give the prevalence of each of these.
- Porphyria cutanea tarda: 1 in 13,000 people
- Erythropoietic protoporphyria: 1 in 43,000 people
- Variegate porphyria: 1 in 244,000 people
What does porphyria cutanea trade (PCT) type 1 occur due to’?
A liver disease that causes reduced activity of the enzyme uroporphyrinogen decarboxylase
This is an acquired form of the disease, not inherited
What enzyme malfunctions in porphyria cutanea tarda type 1?
Uroprophyrinogen decarboxylase
What does Uroprophyrinogen decarboxylase convert?
Uroporphyrinogen III TO Coprophyrinogen III
What are the 2 steps in the diagnosis of PCT?
1 – diagnosis of PCT
2 – diagnosis of the cause(s) of PCT
What skin layer does PCT disrupt?
DEJ
Outline the typical presentation of PCT. Why?
BLISTERS AND FRAGILITY
Because it affects the DEJ
Outline some other features that may be present in PC.
Hyperpigmentation
Hypertrichosis
Solar urticaria
Morphoea
What is morphoea also known as? What is it
Localised scleroderma/ circumscribed scleroderma
Involves isolated patches of hardened skin
How is suspected PCT investigated?
Using a Woods lamp – 410nm violent light shined onto samples, giving fluorescence
Suggest possible underlying causes of PCT (remember that it is due to liver disease).
- Alcohol
- Viral hepatitis
- Oestrogens
- Haemochromatosis