Chapter 5 Neurocutaneous disorders
1. What are the two main forms of neurofibromatosis?
Neurofibromatosis type 1 (NF-1 or von Recklinghausen’s disease) and neurofibromatosis type 2 (NF-2). NF-1 accounts for 90% of all cases of neurofibromatosis and affects approximately 1 in 3500 individuals. NF-2 is a genetically distinct entity with a prevalence of 1 in 25,000. Both conditions have autosomal dominant inheritance with 50% of cases representing new mutations.
2. Outline the diagnostic criteria for NF-1.
The diagnosis can be made if two or more of the following criteria are present:
• Six or more café-au-lait macules >5 mm in greatest diameter in prepubertal children and >15 mm diameter in postpubertal individuals
4. What is the earliest skin sign of NF-1?
Café-au-lait macules. These sharply defined, light brown patches may be present at birth but more commonly start appearing in the first year of life (Fig. 5-1). They are noted initially by 4 years or less in all affected children and within the first year in 82% of cases.
Boyd KP, Korf BR, Theos A: Neurofibromatosis type 1, J Am Acad Dermatol 61:1–14, 2009.
5. What is Crowe’s sign? When does it develop?
Crowe’s sign is freckling of the axillae or other body folds. It develops in 90% of NF-1 patients, usually in middle childhood. These lesions are not really freckles, but multiple small café-au-lait macules.
Key Points: Neurocutaneous Disorders
2. Multiple café-au-lait macules are the earliest skin sign of NF-1, occurring in approximately 80% of affected babies by the end of the first year of life.
3. NF-2 most commonly presents with deafness or tinnitus related to underlying vestibular schwannomas.
6. When do peripheral neurofibromas appear in NF-1?
Peripheral neurofibromas usually start to develop during puberty but increase in size and number in early adult life. They are soft, pink, or flesh-colored papules, nodules, or tumors distributed mainly over the trunk and limbs (Fig. 5-2). Multiple neurofibromas can develop or existing neurofibromas may enlarge during pregnancy.
7. What is a plexiform neurofibroma?
It is a diffuse, elongated neurofibroma occurring along the course of a nerve, usually the trigeminal or upper cervical nerves. Present in 30% of patients with NF-1, these lesions are mostly congenital. They are often disfiguring, associated with overlying skin hypertrophy, hyperpigmentation, and increased hair (Fig. 5-3).
9. What is the most common central nervous system (CNS) tumor occurring in NF-1?
12. How frequently should patients with NF-1 be assessed? What should this assessment include?
An annual assessment is usually sufficient. The clinical examination should include a blood pressure measurement (hypertension occurs in 6% due to renovascular stenosis or pheochromocytoma) and a full neurologic examination. Children also require a regular eye examination; surveillance for kyphoscoliosis, precocious puberty, and hypogonadism; and regular developmental assessments. Investigations should be guided by symptoms or physical signs.
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