7: Photodermatology and porphyria

Question 1

What is photosensitivity?

Answer 1

Symptoms caused by the exposure of skin to the UV radiation from the sun

Question 2

What is the Fitzpatrick scale?

Answer 2

Scale of skin types and what happens to them upon exposure to the sun (burn vs. tan)

Question 3

What are the porphyrias?

Answer 3

Group of diseases caused by abnormal haem metabolism - genetic mutations cause enzyme blocks.

The ones we need to know:

Acute intermittent porphyria (acute attacks, no skin symptoms)

Porphyria cutanea tarda

Erythropoietic protoporphyria (both present as photosensitivity)

Question 4

See OneNote for summaries

Questions of acute intermittent porphyria: https://www.valuemd.com/usmle-step-1-forum/1309-question-stem-5-porphyria-questions.html