Porphyrias

Question 1

what is it?

Answer 1

a group of disorders caused by a build up of natural chemicals which produce porphyrin in the body
Porphyrins are essential for the function of haemoglobin in the body - too much porphyrin (usually because of enzyme deficiency) can cause significant problems

Question 2

what is acute intermittent porphyria?

Answer 2

Caused by porphobilinogen [PBG] deaminase deficiency {PBG deaminase converts PBG into hydroxymethylbilane

Question 3

what causes acute intermittent porphyria?

Answer 3

Inherited (autosomal dominant)

Rare

Question 4

How does acute intermittent porphyria present?

Answer 4

no skin features

can cause neurological symptoms

Question 5

When should acute intermittent porphyria be considered in the differential?

Answer 5

acute abdomen
mononeuritis multiplex
guillain-barre syndrome
psychosis

Question 6

what is porphyria cutanea tarda (PCT)?

Answer 6

• Caused by uroporphyrinogen decarboxylase deficiency

{Uroporphyrinogen decarboxylase converts uroporphyrinogen III into coproporphyrinogen III}

-It is an acquired condition

Question 7

how is PCT managed?

Answer 7

be sure to diagnose PCT and the cause of the PCT
treat underlying diseases,
relieve skin disease, (reduce risk of liver cirrhosis, hepatoma etc.)

Question 8

what causes porhyria cutanea tarda?

Answer 8

usually caused by liver disease (alcohol, viral hepatitis, haemochromatosis), can also be caused by oestrogen
Most common in Scotland

Question 9

how does PCT present?

Answer 9

blisters, 
fragility, 
hyperpigmentation, 
hypertrichosis (abnormal amount of hair growth over the body), 
solar urticaria, 
morphea, 
erosions

Question 10

how is PCT investigated?

Answer 10

urine test - woods lamp

Question 11

what causes erythroproietic protoporphyria?

Answer 11

Caused by ferrochelatase deficiency

{Ferrochelatase converts protoporphyrin IX into haem}

-Inherited - autosomal codominant
Less common

Question 12

How does erythroproietic protoporphyria present?

Answer 12

NOT MUCH TO SEE,
prickly burning sensation after light exposure,
slight redness of skin,
maybe little scars,
also tend to get mild anaemia
Can CAUSE liver disease e.g. liver failure

Question 13

how is erythroproietic protoporphyria investigated?

Answer 13

quantitive RBC porphyrias, 
RBC fluorescent test (patient and relatives), 
transaminases, 
haemoglobin, 
red cell indices, 
biliary tract USS, 
phototesting

Question 14

how is erythroproietic protoporphyria managed?

Answer 14

NOT CURABLE unless you do bone marrow transplant which is usually not justified
-explain diagnosis (genetic counselling),

• Prophylactic TL-O1 [UVB] phototherapy,
• Anti-oxidants
• Visible light photo protection measures (not just UV, especially protect if surgery, avoid middle of day sunlight, clothing, shade, topical sunscreen),
• AVOID IRON
• 6 monthly LFTs and RBC porphyrins,