INTRODUCTION: Idiopathic palmoplantar hidradenitis is an uncommon neutrophilic dermatosis, occurring in children and young adults. Its pathogenesis is incompletely understood. It is characterized by spontaneous resolution, but it can relapse in 50% of cases. We describe a case of a child with atypical idiopathic hidradenitis remarkable for its impact on his motor development. OBSERVATION: A 3-year-old boy was admitted to the pediatric unit for etiological assessment of delayed walking. Medullary MRI and TSH were normal. He was referred to a dermatologic consultation for recurrent and painful palmoplantar lesions, giving an equinus antalgic posture. Examination found erythematous tender plantar nodules. The palms were not affected. The exam was otherwise normal. Diagnosis of idiopathic plantar hidradenitis, pressure urticaria, and plantar erythema nodosum were discussed, leading to a skin biopsy. The histopathologic findings of nodular, neutrophilic infiltrates around the eccrine glands confirmed the diagnosis of idiopathic plantar hidradenitis. Anti-inflammatory treatment was given, followed by complete resolution of the lesions, but persistent equinus posture. COMMENTS: Idiopathic palmoplantar hidradenitis is an uncommon neutrophilic dermatosis, distinct from neutrophilic eccrine hidradenitis. It corresponds to neutrophilic infiltrates of the eccrine sweat glands. It is more frequently reported in children and young adults with no medical history. Its pathogenesis is not completely explained. The lesions are usually painful, hindering walking for a few days or even delaying it, as for our patient. These lesions typically involute, but they may recur in more than half of the cases. CONCLUSION: Through this observation, we highlight the atypical impact of idiopathic hidradenitis and the value of a dermatological examination in case of delayed walking.