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Neurocutaneous disorders are a heterogeneous group of genetic conditions affecting both the central and peripheral nerves that can result in brain, spine, skin, and skeletal manifestations. This chapter discusses select neurocutaneous disorders, or phakomatoses, in which seizures are not a typical component. Neurocutaneous disorders with prominent neurologic features, particularly seizures, are discussed separately (see Chapter 567). A comprehensive table of neurocutaneous disorders (Table 176-1) and selected more commonly observed conditions are described below.
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NEUROFIBROMATOSIS TYPE 1
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CLINICAL MANIFESTATIONS
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Neurofibromatosis type 1 (NF1, Online Mendelian Inheritance in Man [OMIM] no. 162200) is the most common neurocutaneous disorder, and one of the most common autosomal dominant disorders affecting approximately 1 in 3000 people worldwide. The hallmark features of NF1, café-au-lait macules and benign cutaneous neurofibromas, typically arise in early childhood and adolescence, respectively. Approximately two-thirds of individuals with NF1 have manifestations that generally do not require clinical intervention, whereas the remaining one-third display a myriad of medical complications that are unpredictable, both in timing and severity.
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Even though NF1 has been recognized as von Recklinghausen disease by the medical community since the 19th century, both its variability and the age-dependent penetrance of its clinical manifestations made it essential to develop a well-accepted set of clinical criteria to establish the diagnosis (Table 176-2). The typical clinical manifestations allow the diagnosis to be established in children by 8 years according to a set of clinical criteria known as the National Institutes of Health (NIH) consensus criteria for NF1. By virtue of full penetrance in the adult population, diagnosis of NF1 is more straightforward in familial cases because it requires only 1 physical manifestation in addition to an affected first-degree relative. In sporadic cases, features associated with NF1 that are not part of the diagnostic criteria sometimes appear prior to the development of a second diagnostic sign, for example, characteristic T2 hyperintensities on brain magnetic resonance imaging (MRI).
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