Piebaldism-Waardenburg syndrome: histopathologic evidence for a neural crest syndrome

Piebaldism, an autosomal dominant trait, is characterized by patchy hypopigmentation of the face, anterior chest, abdomen, and limbs, heterochromia/bicolored irises, congenital megacolon, and deafness. A 4-month-old Inuit (Eskimo) boy with these manifestations also had left pulmonic artery stenosis, ocular ptosis, and unilateral duplication of the renal collecting system. Evidence is presented for both qualitative and quantitative derangement of neural crest derivatives in this syndrome. Histologically, hypoganglionosis, hyperganglionosis, and ectopic ganglia in lamina propria (neuronal colonic dysplasia [NCD]) were documented in the rectum. The appendix, proximal to the clinical transition zone, showed similar dysplasia. In the hypopigmented skin, multiple microscopic sections were devoid of melanocytes, with no melanin in adjacent basal cells. The hyperpigmented skin contained melanin throughout the basal layer, but the melanocytes were unevenly distributed. Most tissues affected in this boy are of neural crest origin; pathogenesis could be due to faulty migration along the established pathways involving either the borders (basal laminae) or the components of the extracellular matrix (fibronectin, cytotactin, laminin, glycosaminoglycans, and collagen). The similarities between piebaldism and the Waardenburg syndromes are discussed.