Valproic Acid Monotherapy Induced Longitudinal Melanonychia

A 17-year-old male developed longitudinal melanonychia, characterized by brown-black bands on his fingernails and toenails, after 2 years of sodium valproate monotherapy for seizure disorder. This rare side effect, previously undocumented for valproic acid, was confirmed through clinical examination and nail matrix biopsy, which ruled out other causes such as melanoma and infections. The pigmentation, which appeared 3 months after starting the drug, is typically reversible upon drug cessation. This case adds to the limited literature on valproic acid-induced melanonychia, highlighting the need for awareness of this potential adverse effect.