This battle will focus on 2 acute porphyrias (acute intermittent and variegate) and 1 chronic (porphyria cutanea tarda).
1. Acute intermittent porphyria
Acute intermittent porphyria is an autosomal dominant condition in which there is a defect in porphobilinogen deaminase
Females aged 20-40 are most affected.
There is always raised urinary porphobilinogen and aminolaevulinic acid, but the rise is greater during acute attacks. The importance of these substances is that the urine goes deep red on being left.
Signs and symptoms include:
- abdominal pain
- hypertension
- low sodium
- low potassium
- hypotonia
- psychosis
- paralysis
- seizures
A way to remember this list is to think of a patient saying to you "oh doctor, my abdo pain is giving me high blood pressure and stopping me being able to stand (paralysis)"... to which you may think "ah yes, you are a teaspoon (tsp = low tone, sodium, potassium) of crazy (psychosis) aren't you?"
Drugs that can precipitate acute porphyria include:
- alcohol
- benzos
- rifampicin
- tetracyclines
- phenytoin
- OCP
- halothane
- sulphonamides
Treatment is:
- remove precipitating factores
- IV fluid to correct low sodium/potassium
- high carb diet
- IV haematin
- prochlorperazine for nausea
- other symptomatic treatment
Although a rare diagnosis, porphyria should always be a differential in someone presenting with abdominal pain.
2. Variegate porphyria
This is an autosomal dominant condition characterised by a deficit in protoporphyrin oxidase.
It can cause abdominal pain and neuro symptoms, but in contrast to acute intermittent porphyria it also has a photosensitive blistering rash.
It is commoner in South Africans (afrikaans)
3. Porphyria Cutanea Tarda
This is due to uroporphyrinogen decarboxylase deficiency.
It results in a photosensitive rash with bulla.
It is also associated with hypertrichosis.
(these two factors may be the basis of werewolf legends...)
Urine has raised uroporphyrinogen which glows pink under a Woods light
Attacks are precipitated by alcohol, iron and oestrogen.
Treatment is with chloroquine.
Wow, that was quite long. The next battle is far shorter, and is on the second condition I'd never heard of before today...
