Porphyria

Question 1

Porphyria

Answer 1

Porphyrias are a group of disorders caused by genetic or acquired deficiencies in one of the enzymes in the metabolic pathway for haem
Haem precursors (porphyrins) accumulate and react with light to produce skin problems

Question 2

Most common porphyria

Answer 2

Porphyria cutanea tarda

Question 3

Enzyme deficiency in porphyria cutanea tarda

Answer 3

Decreased uroporphyrinogen decarboxylase in the liver

Question 4

Causes of porphyria cutanea tarda

Answer 4

Alcohol
Smoking
Oestrogens
Hep C
Iron overload/haemochromatosis
HIV

Question 5

Presentation of porphyria cutanea tarda

Answer 5

Vesicles/bullae in sun exposed sites
Skin fragility
Hyperpigmentation
Hypertrichosis (abnormal hair growth)
Solar urticaria (urticaria caused by the sun)
Morphoea (patches of hardened skin)

Question 6

Wood’s lamp in porphyria cutanea tarda

Answer 6

Shows excess porphyrins in the urine

Causes pink fluorescence

Question 7

Complications of porphyria cutanea tarda

Answer 7

Hepatocellular carcinoma

Question 8

Treatment of porphyria cutanea tarda

Answer 8

Establish and treat underlying problem

Chloroquine (to remove excess porphyrins from liver)

Question 9

Enzyme deficiency in erythropoetic protoporphyria

Answer 9

Deficiency in ferrochelatase

Causes high levels of protoporphyrin in RBCs, plasma, skin and liver
Autosomal dominant inheritance

Question 10

Presentation of erythropoetic protoporphyria

Answer 10

Prickly, burning pain when exposed to light
Erythema, urticaria and/or swelling
Repeated exposure: lichenification, hypopigmentation, hyperpigementation, scarring

Question 11

Investigations of erythropoetic protoporphyria

Answer 11

RBC porphyrins
Detection of plasmatic fluorescence peak at 634nm
Transaminases
Genetic testing

Question 12

Complications of erythropoetic protoporphyria

Answer 12

Gallstones

Liver failure

Question 13

Treatment of erythropoetic protoporphyria

Answer 13

Genetic counselling
6 monthly LFTs and RBC porphyrins
Photoprotection
Monitor for cholestasis and progressive liver damage
Prophylactic phototherapy
Anti-oxidants
Iron avoidance
Not curable unless you can do a bone marrow transplant which isn't often justified

Question 14

Enzyme deficiency in acute intermittent porphyria

Answer 14

Deficiency in porphobilinogen deaminase

Autosomal dominant inheritance

Question 15

Acute attack precipitants in acute intermittent porphyria

Answer 15

Medication (barbiturates, oral contraceptives)
Alcohol
Infection

Question 16

Presentation of acute intermittent porphyria

Answer 16

Skin is unaffected
Many people are asymptomatic
Acute attack: abdominal pain, vomiting, tachycardia
Severe acute attack: seizures, psychosis

Question 17

Investigations for acute intermittent porphyria

Answer 17

Urine and serum show raised porphobilinogen

Question 18

Complications of acute intermittent porphyria

Answer 18

Liver cancer

Renal failure

Question 19

Treatment of acute attack in acute intermittent porphyria

Answer 19

Hematin and heme arginate is treatment in acute attack