Neurofibromatosis type 1
The most common type of neurofibromatosis. it is characterized clinically by cutaneous and subcutaneous tumors with patches of hyperpigmentation. The hyperpigmented skin areas, are present from birth and found anywhere on the body surface. they can vary markedly in size and color. the dark brown areas are called cafe-au-lait spots. The multiple cutaneous and subcutaneous tumors are nerve sheath tumors, called neurofibromas. they can develop anywhere along the peripheral nerve fibers. Neurofibromas can become quite large, causing a major disfigurement, eroding bone, and compressing various peripheral nerve structures. type 1 neurofibromatosis has dominant inheritance, with a gene locus on the proximal long arm of chromosome 17.