We present a 47-year-old man with a sudden eruption of more than 100 reddish-brown papules, which histologically exhibited a dense dermal proliferation of large mononuclear cells with vesicular nuclei and abundant pale cytoplasm. Electron microscopy and immunohistochemistry revealed findings consistent with indeterminate cell histiocytosis and the patient responded well to treatment with narrowband UVB therapy.

Las histiocitosis son un heterogéneo grupo de enfermedades que se caracterizan por la proliferación de histiocitos en los diferentes tejidos. Actualmente se clasifican en tres grupos: I) Histiocitosis de células de Langerhans; II) Histiocitosis de células no Langerhans; e III) Histiocitosis malignas. Presentamos el caso de un varón de 12 años con pápulas normocoloreadas, múltiples y generalizadas de años de evolución. Se realizó un análisis sangre, orina y un estudio de extensión cuyos resultados estuvieron dentro de la normalidad. La biopsia mostró abundantes histiocitos positivos para CD68, factor XIIIa y negativos para S-100 y CD1a. Basándonos en el cuadro clínico y las pruebas complementarias se estableció el diagnóstico de Histiocitosis eruptiva generalizada (HEG). La HEG es una entidad muy rara que afecta principalmente a la población adulta. Clínicamente se manifiesta como cientos de pápulas distribuidas por cara, tronco y extremidades, de carácter autoinvolutivo, por lo que no suele requerir tratamiento.

Dermatofibromas are benign, fibrohistiocytic, dermal tumors. Solitary dermatofibromas may be incidental findings, whereas multiple dermatofibromas may be associated with systemic conditions or previous therapies. Two women and one man with multiple dermatofibromas and an associated systemic condition, immunosuppression, or both, are described. Nine dermatofibromas developed in a woman with hypothyroidism, optic neuritis, and Arnold Chiari I malformation. Five dermatofibromas developed in a woman with breast cancer who had received several systemic antineoplastic therapies. Eleven dermatofibromas developed in a man with HIV whose systemic therapies included acyclovir, darunavir/cobicistat, dolutegravir, etravirine, and ritonavir. Conditions associated with multiple dermatofibromas include autoimmune diseases, cancer, chromosomal abnormalities, immunodeficiencies, metabolic disturbances, and altered physiologic states such as pregnancy. Medications received by patients with multiple dermatofibromas included immunosuppressive agents, psoriasis therapies, and antineoplastic drugs. Multiple dermatofibromas can be observed in patients with associated medical conditions, systemic therapies, or both. Therefore, in individuals presenting with multiple dermatofibromas, not only evaluation for associated disorders, but also review of prior and current drug therapies, should be considered.