Rosacea: what if you were simply treating a Sign of Demodicosis ?

• Demodicosis is a disease in itself due to the presence of the mite Demodex folliculorum first classied as such in 1842 by the German dermatologist Carl Gustav Theodor Simon.

• It is easily confused with Rosacea (Acne Rosacea) because the latter, although considered to be associated with the presence of the mite, is controversial and an causal relationship has yet to be demonstrated.

Primary demodicosis is the condition itself and is classified in the following way:

• pityriasis folliculorum (change proposal: spinulate demodicosis)
• Rosacea-like (rosaceiform) demodicosis, perioral/periorbital/periauricular dermatitis-like demodicosis (change proposal: Papulopustular demodicosis, perioral demodicosis, periorbital demodicosis,periauricular demodicosis)….this is where rosacea and perioral dermatitis may be diagnosed when in fact it is a demodex-induced dermatosis.
• Demodex abscess/facial abscess-like conglomerates (change proposal: Nodulocystic/conglobate demodicosis)

Secondary demodicosis is the presence of the mite secondary to a skin condition or a systemic disease and is classified as such:

• Inflammatory skin disease: perioral dermatitis, papulopustular rosacea, seborrheic dermatitis, steroid-induced dermatitis.
• Treatment-associated diseases
• Tumors
• Systemic diseases

Such classifications might be considered as being a bit complicated but it might help to finally understand that treatment of diagnosed « perioral dermatitis, rosacea »… which do not respond might be in fact demodecidosis and that the latter responds to acaricidal substances (although evidence is somewhat limited)

-oral ivermectin

-topical permethrin 5%, benzyl benzoate 10–25%, crotamiton 10%, lindane 1% or malathion 0.
5%

Contributors

Dr Christophe Hsu – dermatologist. Geneva, Switzerland

Article selection: Prof Dr Jean-Hilaire Saurat – dermatologist. Geneva, Switzerland

Source of information: Human demodicosis: revisit and a proposed classification. Chen W, Plewig G. Br J Dermatol. 2014 Jun;170(6):1219-25. doi: 10.1111/bjd.12850.