Photodermatology + Porphyrias Flashcards
What is the definition of photosensitivity?
Which areas of the body are affected?
What are the two main types?
Photosensitivity denotes conditions triggered by light. Rashes affect sun exposed areas e.g. face, “v” of neck, dorsum of hands and arms. They may be primary (rare, e.g. cutaneous porphyrias) or acquired, e.g. drug induced photosensitivity.
What is the most common category of cutaneous photosensitivity?
Give some examples
The most common category of cutaneous photosensitivity is idiopathic and includes conditions such as:
- Polymorphic light eruption (PLE – most common)
- Chronic actinic dermatitis (CAD)
- AP
What is polymorphic light eruption?
Who does it commonly affect and when?
Symptoms?
When is it better?
Polymorphic light eruption is a common idiopathic disorder typically affecting young women in spring. After light exposure, itchy red papules, vesicles and plaques develop on expose sites, fading after 1-6 days. It often improves over the summer due to a phenomenon called “hardening”.
Give some treatment options for polymorphic light eruption
- Behavioural avoidance, clothing, sunscreen use
- Hardening phototherapy
- Chromophore removal
- Inhibition of mediator/action release
- Inhibition of inflammatory response
What is a porphyria?
Porphyria refers to a group of disorders that result from a build-up of natural chemicals that produce porphyrin in your body. Porphyrins are essential for the function of hemoglobin – there are lots of different intermediate porphyrias in the formation of haemoglobin.
What are the four main groups of prophyria?
- Phototoxic skin porphyrias (such as erythropoietic protoporphyria)
- Blistering and fragility skin porphyrias
- Acute attack porphyrias (some with no skin involvement; some also cause blistering and fragility)
- Severe congenital porphyrias (such as congenital erythropoetic porphyria)
What are the two main skin features of porphyrias?
Blistering and fragility of the skin
What is the commonest prophyria?
- Pathophysiology?
- What are the two steps of diagnosis?
- Clinical presentation?
Porphyria cutanea tarda type 1
- Reduced enzyme activity of uroporphyrinogen decarboxylase results in overproduction of photo-active porphyrins.
- There are two steps in the diagnosis – diagnosis of PCT itself and diagnosis of the cause(s) of PCT.
- The typical presentation is blisters and fragility, but can also get hyperpigmentation, hypertrichosis, solar urticarial and morphoea.
Investigations – Woods lamp
Give four possible causes of pophyria cutanea tarda 1
What is the aim of treatment of this condition?
- Alcohol
- Viral hepatitis
- Oestrogens
- Haemochromatosis
The aim of treatment is to relieve the skin disease and treat the underlying diseases in order to reduce the risk of liver cirrhosis, hepatoma etc.
Erythropoietic protoporphyria
- Pathophysiology?
- Symptoms?
- Signs?
- Complication?
There is a build up of a porphyrin (protoporphyrin) in the blood, especially in red blood cells.
Exposure to sunlight causes tingling, itching or burning which may be associated with redness or swelling. Symptoms usually occur within a few minutes of skin exposure to sunlight, and often take hours or days to resolve.
Despite severe discomfort there may be northing abnormal to see on the skin. Sometimes there can be swelling like a nettle rash. Skin can also harden over time.
Occasionally it can lead to liver damage, so LFTs are monitored 6 monthly.
Erythropoietic protoporphyria
- What prophylactic therapy should the patient receive?
Treatment of incipient liver failure?
Treatment of liver failure?
The patient should receive prophylactic TL-01 phototherapy, antioxidants, and be advised to avoid iron.
If incipient liver failure occurs then give oral charcoal, cholestyramine.
If liver failure occurs, then consider liver transplant or bone marrow.
