Piebaldism is genetic defect in melanocyte development that results in patches of hypopigmented skin and hair. Phenotypically, the Piebald trait is characterized by a white hair forelock, and stable areas of hypopigmentation on the anterior trunk and extremities, in the absence of extracutaneous manifestations. The pathogenesis of this disease is not clearly known. However, evidence suggests that a failure of embryonic migration or proliferation by primitive melanoblasts leads to areas devoid of melanocytes.

Studies have shown mutations in the human C-Kit protooncogene to be causal for the human piebald trait. Homologues of this gene are also known to be responsible for piebaldism in other animals. The effect is likely to be a dominant negative one, impairing receptor activity. Heterozygous mutations in the SNAI2 (Snail Family Transcriptional Repressor 2) gene is also known to cause piebaldism.