Acne and Rosacea Charity Training Manual

Pathogenesis of Rosacea
The pathogenesis of rosacea is unclear but a number of hypotheses have been proposed.
1. Rosacea is associated with Helicobacter pylori infections and may be associated with gastrointestinal symptoms. It has been shown that type II
rosacea will improve when patients are treated for H pylori eradication, but this is most likely to be due to the anti-inflammatory effects of the
antibiotics used in this condition and the rosacea relapses once the antibiotics are stopped
2. Rosacea is caused by the demodex mite, Demodex folliculorum. Demodex are a commensal in the skin. In some situations, the density of demodex
increases, mainly due to the use of cream cleansers of the skin and avoidance of soap and water which would normally reduce the level of
demodex. Studies have shown that systemic ivermectin, which clears the skin of demodex mites led to no improvement in rosacea.
3. Rosacea is caused by an abnormality of one of the skin’s antimicrobial peptides. The skin produces a series of naturally occurring antibiotics, the
antimicrobial peptides. These are the cathelicidins and the human defensins. Only one cathelicidin is found in human skin LL37. Studies have
shown in patients with rosacea that cathelicidin processing is disturbed resulting in peptide fragments causing inflammation, erythema and
telangiectasias. More work need to be performed on this.
4. Rosacea is caused by an abnormal vascular response in the skin and can be associates with migraine. This is the most plausible proposal. Blood
vessels in the skin form two plexuses parallel to the surface of the skin – the superficial and deep plexuses. Their primary function is to feed and
oxygenate the skin but the maximal blood flow through the skin is very much higher that the metabolic needs of the skin. The second important
function of the skin vasculature is to cool the body. This is orchestrated via the sympathetic nervous system via receptors in the brain, heart, large
vessels and stomach, which stimulate receptors on the blood vessels – receptors cause vasoconstriction and receptors cause vasodilation. In
rosacea, this system is abnormal leading to flushing. With time, the skin blood vessels become leaky with serous fluid escaping into the dermis,
causing swelling and acting as a focus for inflammation and spot formation.
The fourth proposal is the most likely and gives some direction as to the management of rosacea. The primary abnormality is the vascular instability, with
flushing being the first and cardinal sign of rosacea. This needs to be addressed if rosacea is to be treated properly.
Patient with rosacea have very sensitive skin and patients will often not tolerate a vast array of topical agents including moisturizers and cosmetics. It is
important for patients to try different products to find what their skin will tolerate.
Glossary
• Peptide – a molecule composed of 2 or more amino acids – may result from the breakdown of protein