Introduction to Photodermatology and Porphyrias Flashcards

(41 cards)

1
Q

What is photobiology defined as?

A

The study of non-ionising radiation on living systems

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2
Q

What does photobiology encompass?

A

Botany, zoology, medicine

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3
Q

What are photodermatoses?

A

Skin conditions with an abnormal reaction to light

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4
Q

Shorter wavelengths of light have more ______

A

ENERGY

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5
Q

Longer wavelengths of light have more __________

A

PENETRANCE

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6
Q

Why may sparing of the area of skin behind the ear lead you to suspect photosensitivity?

A

The area of skin behind the ear is not usually exposed ti sunlight/light

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7
Q

Why are there so many different porphyrias?

A

There is a huge range of enzymes in the pathway that converts glycine +succinyl CoA to Haem that can be missing or defective

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8
Q

What is a porphyria?

A

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

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9
Q

Porphyrias are due to abnormal metabolism of ___________

A

HAEMOGLOBIN

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10
Q

Outline the 4 main groups of porphyrias.

A
  1. Phototoxic
  2. Blistering and fragility
  3. Acute attack
  4. Severe congenital
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11
Q

Give an example of a phototoxic porphyria.

A

Erythropoietic protoporphyria

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12
Q

Give an example of a congenital porphyria.

A

Congenital erythropoetic porphyria

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13
Q

Describe what patients with a severe attack porphyria experience on exposure to light.

A

Prickly, burning pain on the exposed areas

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14
Q

What are the 3 most common skin porphyrias in Scotland? Give the prevalence of each of these.

A
  1. Porphyria cutanea tarda: 1 in 13,000 people
  2. Erythropoietic protoporphyria: 1 in 43,000 people
  3. Variegate porphyria: 1 in 244,000 people
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15
Q

What does porphyria cutanea trade (PCT) type 1 occur due to’?

A

A liver disease that causes reduced activity of the enzyme uroporphyrinogen decarboxylase

This is an acquired form of the disease, not inherited

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16
Q

What enzyme malfunctions in porphyria cutanea tarda type 1?

A

Uroprophyrinogen decarboxylase

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17
Q

What does Uroprophyrinogen decarboxylase convert?

A

Uroporphyrinogen III TO Coprophyrinogen III

18
Q

What are the 2 steps in the diagnosis of PCT?

A

1 – diagnosis of PCT

2 – diagnosis of the cause(s) of PCT

19
Q

What skin layer does PCT disrupt?

20
Q

Outline the typical presentation of PCT. Why?

A

BLISTERS AND FRAGILITY

Because it affects the DEJ

21
Q

Outline some other features that may be present in PC.

A

Hyperpigmentation
Hypertrichosis
Solar urticaria
Morphoea

22
Q

What is morphoea also known as? What is it

A

Localised scleroderma/ circumscribed scleroderma

Involves isolated patches of hardened skin

23
Q

How is suspected PCT investigated?

A

Using a Woods lamp – 410nm violent light shined onto samples, giving fluorescence

24
Q

Suggest possible underlying causes of PCT (remember that it is due to liver disease).

A
  • Alcohol
  • Viral hepatitis
  • Oestrogens
  • Haemochromatosis
25
What are the 2 main aims of PCT treatment?
- Relieve the skin disease | - Treat the underlying skin diseases, to reduce the risk of liver cirrhosis, hepatoma etc
26
What is erythropoietic protoporphyria caused by?
A deficiency of the enzyme Ferrochelatase which is responsible for the conversion of Protoporphyrin IX to Haem
27
Describe the inheritance of erythropooietic protoporphyria.
Autosomal co-dominant
28
Outline the presentation of erythropooietic protoporphyria.
Starts off like chicken pox/abnormal sensitivity to sun Sun causes tingling, itching or burning, red, swelling
29
How long after sun exposure will erythropooietic protoporphyria develop?
After a few minutes and can often last for days
30
People with EPP are often more sensitive to ___________
TEMPERATURE
31
When does EPP usually start?
Childhood
32
What investigations are used to aid in the investigation of suspected porphyrias?
``` Quantitative RBC porphyrins Fluorocytes (patient, relatives) Transaminases [Hb], red cell indices (Biliary tract USS) (Phototesting) ```
33
How is erythropoietic porphyria managaed?
1. Explain diagnosis + council 2. 6 monthly LFT's and RBC's 3. Visible light porto-protection measures
34
What can EPP be cured by? Is this worth the risk?
Bone marrow transplant - NO
35
What can be given as prophylaxis in EPP?
TL-01 phototherapy
36
What is the start of liver failure in EPP treated with?
Oral charcoal, cholestyramine, ALA synthase inhibition
37
What is end stage liver failure in EPP treated with?
Liver transplant | Bone marrow transplant
38
What is the 'sun-burning' part of the electromagnetic spectrum?
UVB light
39
Give examples of photo-protection measures.
* Behavioural (e.g. avoid middle of day sunlight) * Clothing (importance of weave, colour, etc) * Environmental (e.g. shade trees, window films) * Topical sunscreen (not good at protecting from visible light as this needs to be reflected away)
40
What are porphyrins?
The building blocks of haem, which, when combined with a protein (globin), forms haemoglobin
41
What is the role of porphyrins in EPP?
In the case of EPP, there is a build-up of one of these porphyrins (protoporphyrin) in the blood, especially in the red blood cells This leads to a sensitivity to sunlight