Stem cell factor (SCF) stimulates the proliferation of mast cells. SCF augments the proliferation of both myeloid and lymphoid hematopoietic progenitors in bone marrow culture. SF mediates cell-cell adhesion. Defects in SCF are the cause of familial progressive hyperpigmentation (FPH), also called melanosis universalis hereditaria (MUH). FPH is an autosomal-dominantly inherited disorder characterized by hyperpigmented patches in the skin, present in early infancy and increasing in size and number with age.