ABSTRACT
This chapter reviews rare disorders with generalized diffuse pigmentary dilution. These syndromes with multisystemic abnormalities are usually due to mutations of genes responsible for the production of melanin or the processing of melanosomes, and hypopigmentation of the skin and hair is present. During embryogenesis, progenitor melanoblasts migrate between mesodermal and ectodermal layers to reach their final destinations in the epidermis and hair follicular bulbs, as well as the inner ear cochlea, choroids, ciliary body, and iris. Any disorder that destroys the melanocytes in the skin also affects other organs and systems. Rare disorders with common hypopigmentation but different systemic signs like Alezzandrini syndrome, Margolis syndrome, Cross syndrome, Hermansky–Pudlak syndrome, Vici syndrome, Chediak-Higashi syndrome, and Griscelli syndrome will be discussed in this chapter. For example, the presence of bleeding diatheses may be a sign of Hermansky–Pudlak syndrome, immune deficiency points to Chediak–Higashi syndrome, and structural ocular and neurological abnormalities suggest Cross syndrome.
