What Vitamin Deficiency Causes Brown Lines on Nails? Uncovering the Truth
                                
                                
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                                    4 min read                                
                            
                                Over 50% of all cases of nail discoloration are caused by a condition called melanonychia, which manifests as a brown or black stain on the nail plate. While often benign, the potential causes range from trauma to systemic illnesses, including what vitamin deficiency causes brown lines on nails.