Neurofibromatosis and Tuberous Sclerosis

Published on 05/03/2015 by admin

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Last modified 05/03/2015

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Neurofibromatosis and Tuberous Sclerosis

• Neurofibromatosis (NF) and tuberous sclerosis (TS) are neurocutaneous disorders (phacomatoses) characterized by skin lesions as well as neoplasms of the central and peripheral nervous systems.

• Cutaneous manifestations (especially pigmentary findings) are often the first clinical signs of NF type 1 (NF1) and TS.

• Both disorders have autosomal dominant inheritance, although ~30–50% of patients have unaffected parents and harbor new, spontaneous mutations.

• Education of patients/parents about the condition, attention to psychosocial concerns, and genetic counseling represent important components of care.

Neurofibromatosis Type 1 (von Recklinghausen Disease)

• Incidence of approximately 1 in 3000 births.

• The NF1 tumor suppressor gene encodes the neurofibromin protein, which negatively regulates the RAS-mitogen-activated protein kinase (MAPK) pathway that promotes cell survival and proliferation.

• Patients with NF1 have a constitutive (germline) NF1 mutation plus a somatic ‘second hit’ mutation inactivating the other copy of the gene in affected tissues (e.g. Schwann cells in neurofibromas, melanocytes in café-au-lait macules [CALMs]).

• The major clinical features of NF1 are outlined in Table 50.1 and depicted in Figs. 50.1–50.5; Fig. 50.6 shows the time course of their development.

Fig. 50.1 Café-au-lait macules and ‘freckling’. Oval-shaped, light-to medium-brown patches with regular borders and uniform pigmentation (A, B). Numerous 1- to 3-mm lentigines are most commonly found in the axilla (Crowe’s sign) (B) but can also develop in other sites such as the perioral region (C). A, C, Courtesy, Julie V. Schaffer, MD.

Fig. 50.2 Multiple cutaneous neurofibromas. Soft, skin-colored to pinkish tan, dome-shaped or polypoid, well-demarcated papules and nodules of various sizes (A, B) in patients with NF1. Neurofibromas may be superimposed on café-au-lait macules and lentigines (B). Courtesy, Julie V. Schaffer, MD.

Fig. 50.3 Spectrum of cutaneous neurofibromas. Lesions range from subtle blue-red macules (A) to exophytic nodules with associated hypertrichosis (B). Courtesy, Julie V. Schaffer, MD.

Fig. 50.4 Plexiform neurofibromas. A A hyperpigmented plaque that may be misdiagnosed as a congenital melanocytic nevus or (if not palpated) a café-au-lait macule. Note the widespread ‘freckling’ on the trunk. B A poorly circumscribed, sagging pink mass. Courtesy, Julie V. Schaffer, MD.

Fig. 50.5 Lisch nodules. Multiple yellow-brown papules of the iris.

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