ABSTRACT

Tradition holds that the varied disorders collectively referred to as the phakomatoses be discussed together. However, from a genetic, developmental, and clinical standpoint, the designation has limited usefulness, as can be deduced from efforts to define the term (130,131,145). The phakomatoses comprise a heterogenous group of diseases that feature widespread, tumor likemalformations (130,242) consisting of tissue components normally found at the involved site (hamartomas) (5,251). The hamartomas are usually congenital and tend to involve the central nervous system (CNS), retina, and skin, and thus the conditions are also referred to as the “neurocutaneous syndromes” (2,254). The label “phakomatoses,” derived from the Greek root for “mother spot” or birthmark, was introduced in 1932 by van der Hoeve (130), who substituted the term “phakoma” in preference to the designation “nevus,” which pathologists had previously applied to these conditions (234,235). Originally, three entities were included under the classification of phakomatosis: angiomatosis retinae [von Hippel-Lindau disease (VHLD)]; neurofibromatosis (NF); and tuberous sclerosis (now called tuberous sclerosis complex) (TSC). It is noteworthy that these “original three” phakomatoses have subsequently been shown to develop from mutations in genes involved in the control of cell replication and the suppression of tumor formation (130,145). Thus, scientific discovery established a link between these entities that supports the grouping of at least some of the phakomatoses. However, it is important to realize that the genes involved in VHLD, NF, and TSC differ, and their clinical manifestations are dissimilar (130).