Presence of Demodex spp. on the face and scalp in patients affected by papulopustular rosacea of face.

BACKGROUND

The increased proliferation of Demodex mites in the pilosebaceous unit can be the cause of rosacea flare-ups on the face. Signs and symptoms of the scalp (e.g., itching, dandruff) have sometimes been reported in patients with papulopustular rosacea of face; they may be due to a proliferation of Demodex mites on the scalp.

METHODS

To study the Demodex mites count, a standardized skin surface biopsy was performed on the cheek and on the scalp. Microscopic examination and molecular identification of Demodex were performed. Pearson's χ2 Test or Fisher's Exact Test were used to test for any association between categorical variables and outcome.

RESULTS

Patients affected by papulopustular rosacea had a greater frequency of Demodex-positive standardized skin surface biopsy than controls at the scalp (35.0% vs. 0%, P=0.033), at the face and/or at the scalp (50% vs. 10%, P=0.032). Demodex positive patients with a Demodex-positive face sample were more frequently found to have a Demodex-positive scalp sample (P=0.035). The predominant species was found to be Demodex folliculorum (92.6% of samples); the species Demodex brevis was identified only in 7.4% of samples.

CONCLUSIONS

Demodex folliculorum is more frequently found on the scalp and face of patients with rosacea than controls, even though it is not statistically associated with scalp symptoms. The scalp may be a reservoir area for Demodex mites which could migrate on the face again after an acaricidal treatment.