MORPHOLOGY

Clinically, acne can present as non-inflammatory or inflammatory lesions or both. Non­inflammatory acne is marked by the presence of codemos. Codemos are follicular-based papules that may be either open or closed. Open codemos, commonly called blackheads, are papules with prominent dilated follicular ostia. Closed codemos, or whiteheads, are flesh colored papules without an evident follicular opening. Inflammatory acne can include lesions such as erythematous papules, pustules, nodules, cysts, or plaques. Post-inflammatory hyper – or hypopigmentation are common sequelae of inflammatory acne. However, scarring can be a complication of both inflammatory and non-inflammatory acne.