Tender, plantar nodules occurring in pediatric patients can be associated to different clinical entities, despite similar morphological features, therefore dermatopathology is the best technique for the definitive diagnosis. We describe the case for a 12-year-old patient with tender, red nodules on the left sole 3 days in duration, and with moderate functional disability. The onset of the lesions was preceded by low fever, and occurred 6 days after hepatitis B vaccination (Engerix B). The clinical diagnoses were juvenile plantar erythema nodosum, insect bites, pressure urticaria and plantar hidradenitis; Laboratory and radiographic studies, as well as microscopic examination of a skin biopsy specimen, were performed. The lesions resolved spontaneously in about 10 days, without recurrence after a year. A skin biopsy specimen revealed dense neutrophilic infiltrate surrounding and involving eccrine glans with abscess formation at the dermal-hypodermal junction. The diagnosis of idiopathic plantar hidradenitis was made. We discuss this entity, recently described by Stahr et al, and other erythematous plantar nodules in the pediatric age.