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DERMATOLOGY > Introduction to Photodermatology and Porphyrias > Flashcards

Introduction to Photodermatology and Porphyrias Flashcards

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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?

A

DEJ

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
Q

What are the 2 main aims of PCT treatment?

A
  • Relieve the skin disease

- Treat the underlying skin diseases, to reduce the risk of liver cirrhosis, hepatoma etc

26
Q

What is erythropoietic protoporphyria caused by?

A

A deficiency of the enzyme Ferrochelatase which is responsible for the conversion of Protoporphyrin IX to Haem

27
Q

Describe the inheritance of erythropooietic protoporphyria.

A

Autosomal co-dominant

28
Q

Outline the presentation of erythropooietic protoporphyria.

A

Starts off like chicken pox/abnormal sensitivity to sun

Sun causes tingling, itching or burning, red, swelling

29
Q

How long after sun exposure will erythropooietic protoporphyria develop?

A

After a few minutes and can often last for days

30
Q

People with EPP are often more sensitive to ___________

A

TEMPERATURE

31
Q

When does EPP usually start?

A

Childhood

32
Q

What investigations are used to aid in the investigation of suspected porphyrias?

A 
Quantitative RBC porphyrins
Fluorocytes (patient, relatives)
Transaminases
[Hb], red cell indices
(Biliary tract USS)
(Phototesting)
33
Q

How is erythropoietic porphyria managaed?

A
  1. Explain diagnosis + council
  2. 6 monthly LFT’s and RBC’s
  3. Visible light porto-protection measures
34
Q

What can EPP be cured by? Is this worth the risk?

A

Bone marrow transplant - NO

35
Q

What can be given as prophylaxis in EPP?

A

TL-01 phototherapy

36
Q

What is the start of liver failure in EPP treated with?

A

Oral charcoal, cholestyramine, ALA synthase inhibition

37
Q

What is end stage liver failure in EPP treated with?

A

Liver transplant

Bone marrow transplant

38
Q

What is the ‘sun-burning’ part of the electromagnetic spectrum?

A

UVB light

39
Q

Give examples of photo-protection measures.

A
  • 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
Q

What are porphyrins?

A

The building blocks of haem, which, when combined with a protein (globin), forms haemoglobin

41
Q

What is the role of porphyrins in EPP?

A

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

DERMATOLOGY (6 decks)

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