The appearance of localized acne or comedo reaction during or shortly after radiotherapy is an unusual adverse event, but one that is probably underestimated. It can manifest as an inflammatory (papules, pustules, nodules), comedonal (open and closed comedones, Favre-Racouchot-like syndrome), or mixed presentation. We report two new cases of radiation-induced acne with different clinical aspects and discuss the main known features of this adverse event.

The vast majority of patients treated with radiotherapy develop dermatological side effects. Acute radiation dermatitis or chronic skin fibrosis are well known sequels of radiation, but there are also other infrequent skin toxicities following external radiotherapy we should be aware of. We present a case of a rare form of delayed radiation dermatitis consisting of a localized acneiform eruption, confirmed by skin biopsy, in the irradiated fields in a woman with breast cancer. We review the clinical characteristics and risk factors available in the literature about this unusual adverse effect of radiotherapy. It is important for dermatologists to recognize this rare adverse effect, owing to the important impact on physical and psychosocial health of the patients and because it may delay the surgical reconstruction.

Pseudoxanthoma elasticum (PXE) is an autosomal recessive disorder characterized by atypical elastic fibers that causes connective tissue abnormalities of the skin, eyes, and heart, among other organs. The disorder is rare, with a classic presentation of yellow-orange cobblestone-like papules on flexural areas, lax skin, ocular degeneration, and moribund vasculature in multiple organs. There is wide variability in the presentation of the affected organs [1]. We present two sisters with classic cutaneous findings of PXE with the additional unusual findings of numerous open comedones on the neck. To our knowledge, this is the first report of numerous open comedones in familial PXE.