L’érythème noueux (EN) est la variante clinico-pathologique la plus fréquente des panniculites. Il s’agit d’une hypodermite nodulaire aiguë considérée comme une réaction d’hypersensibilité non spécifique à divers allergènes. Il peut être exceptionnellement secondaire à une infection fongique ou aux traitements antimycosiques. Nous rapportons un cas d’EN faisant suite à un kérion de Celse qui est une teigne inflammatoire et suppurative du cuir chevelu. Dans cette observation, l’EN était apparu avant le début du traitement antimycosique, et s’était spontanément amélioré après le traitement de la teigne.

Erythema nodosum (EN) is the most common clinical and pathological variant of panniculitis. A Celsus kerion is an inflammatory and suppurative tinea of the scalp. We report on a rare case of EN secondary to a kerion of the scalp.

A 9-year-old child without a notable medical history, had a squamous plaque of the vertex for 15 days, which became painful and purulent. Five days after the plaque appeared, he presented with painful, hot, erythematous lesions symmetrically on the extensor surfaces of the legs and forearms. A medical examination found a fever of 38.5°C, a squamous purulent and crusty plate of the vertex (6/5cm) with pustules and a few hairs cut short, and symmetrical painful erythematous hot nodules on the anterior surfaces of the two legs and forearms. A mycological sample of the crusts of the scalp lesion confirmed the presence of Trichophyton mentagrophytes. A bacteriological sample was not taken, and a skin biopsy confirmed the diagnosis of EN. The results of other paraclinical investigations were normal. The diagnosis of EN secondary to an inflammatory scalp tinea was established, and our patient was prescribed an orally and locally administered antimycotic, rest, and elevation of the limbs.

EN is an acute nodular hypodermitis considered a nonspecific hypersensitive reaction to various allergens. Rarely, it can occur secondary to a fungal infection of the scalp such as a kerion or even secondary to the antifungal treatment of this tinea. EN secondary to a kerion of the scalp before the beginning of antifungal treatment has been reported in the literature, with a spontaneous improvement of the EN after treatment of the tinea.