Porphyria

Definition: Group of rare photosensitivity disorders that results from a build-up of chemicals called porphyrins.  Thus, the body cannot produce enough haem, which is an important component of haemoglobin. 

These disorders are typically inherited due to a genetic mutation and are more common in women. Other risk factors for getting porphyria include alcohol, some medications, smoking, and infections like Hepatitis C or HIV. (1)

Different types of porphyria can be divided into acute or cutaneous. Acute porphyria has a quick onset and mostly affect the nervous system. Cutaneous porphyria affects the skin. (2)

This article will cover the 3 main types of porphyria: Acute intermittent porphyria, Porphyria cutanea tarda and Erythropoietic protoporphyria.

Acute intermittent porphyria

This is the most common type of acute porphyria which can be classified as intermittent and recurrent attacks of pain, plus other clinical symptoms. (3) AIP is caused by an autosomal dominant mutation, leading to a deficiency in the enzyme porphobilinogen deaminase. 

Clinical presentation 

• Severe abdominal pain 

• Muscle weakness 

• Seizures 

• Heart palpitations, anxiety, depression

• Dysuria, discoloured urine 

A good way to remember the symptoms is using the 5Ps mnemonic: (4)

• Pain in abdomen

• Polyneuropathy

• Psychological abnormalities

• Pink urine 

• Precipitated by drugs eg. Oral contraceptives 

Investigations 

• Urine tests (elevated PBG levels)

• Genetic testing 

Management 

• Admission to hospital for acute attacks and supportive measures

• Give IV Hemin 

• Lifestyle changes for prevention of future attacks eg. Stop smoking, cut down on alcohol and excessive stress

Porphyria cutanea tarda

This is the most common type of cutaneous porphyria. There is a problem in the enzyme uroporphyrinogen decarboxylase, which causes sensitivity to sunlight. Liver disease is common, due to a build-up of iron. There are 2 types of PCT. Type 1 is acquired/sporadic, whereas Type 2 is genetic. (5)

Clinical presentation 

Figure 1 – Porphyria cutanea tarda (6)

• Painful skin blisters, especially on sun-exposed places like the arms and face 

• Fragile skin 

• Hyperpigmentation 

• Hypertrichosis (excessive hair growth)

Investigations 

• Blood, urine, and stool tests

• Woods lamp (orange red fluorescence) = higher levels of porphyrin

Management 

• Treat the underlying cause first 

• Avoid as much sunlight as possible or wear protective layers 

• Repeated phlebotomy (removal of blood, and thus eventual removal of excess iron) (7)

• Chloroquine / hydroxychloroquine sulfate (low dose)

Erythropoietic protoporphyria

This is the most common type of childhood porphyria. Autosomal dominant mode of inheritance. There is a defect in the enzyme ferrochelatase. 

Clinical presentation 

Figure 2 – Erythropoietic protoporphyria (8)

• Skin swelling 

• Pain after exposure to sun 

• Crusting of the face/hands

• Erythema

• Hyperpigmentation

Investigations 

• Blood tests 

• Genetic testing

Management 

• 6 monthly LFTs and blood tests (RBC porphrins)

• Visible light photoprotection measures eg. phototoxic protective clothing

• Avoid excessive exposure to sunlight

Summary of the different types of porphyria

From Notion notes

References

1. Cleveland Clinic. Porphyria | Cleveland Clinic [Internet]. 2018. 

2. National Institute of Diabetes and Digestive and Kidney Diseases. Porphyria | NIDDK [Internet]. 2019. 

3. Porphyria - Symptoms and causes [Internet]. Mayo Clinic.

4. Porphyria Notes. Osmosis [e-book]. Pgs. 447-450. osmosis.org

5. Porphyria Cutanea Tarda - Hormonal and Metabolic Disorders [Internet]. MSD Manual Consumer Version. 

6. Porphyria cutanea tarda | DermNet NZ [Internet]. dermnetnz.org. Available from: https://dermnetnz.org/topics/porphyria-cutanea-tarda 

7. Porphyria cutanea tarda - Symptoms, diagnosis and treatment | BMJ Best Practice [Internet]. bestpractice.bmj.com. Available from: https://bestpractice.bmj.com/topics/en-gb/234 

8. Erythropoietic protoporphyria | DermNet NZ [Internet]. dermnetnz.org. Available from: https://dermnetnz.org/topics/erythropoietic-protoporphyria 

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