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Neurofibromatosis, Type 1

Neurofibromatosis, Type 1

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Neurofibromatosis, Type 1 (aka, von Recklinghausen disease)
Overview
  • NF-1 is a neurocutaneous disease with numerous neoplastic manifestations.
  • The most common neurogenetic disorder.
    • Incidence of ~ 1/3,000 worldwide
  • 50% of cases are Autosomal Dominant inherited, the remainder are spontaneous.
    • The autosomal dominance has a high penetrance and variable expressivity.
Mutation in chromosome 17 causes a loss of function the neurofibromin tumor suppressor gene. Mnemonic: 17 letters in “von Recklinghausen” helps us remember chromosome 17 = Neurofibromatosis)*.
    • Note that the mechanistic Target of Rapamycin (called: mTOR) is another important factor in the development of NF-1 gliomas (just as it is in tuberous sclerosis complex (TSC)).
Tumors
The following tumors are definitely known to be associated with NF-1 (other tumors are also suspected to have an association with it):
Cutaneous Manifestations & NF-1 Diagnostic Criteria
Two of any of the following is diagnostic:
  • Café-au-lait spots
    • 6 or more. Qualifying sizes - Prepubertal: > 5mm. Postpubertal: > 15mm.
  • Neurofibromas
    • 2 or more of any kind
    • 1 plexiform neurofibroma
  • Axillary or inguinal freckling
  • Optic glioma
  • Iris hamartomas (aka, Lisch nodules)
    • 2 or more
  • Osseous lesion (eg, sphenoid wing dysplasia)
  • First-degree relative with NF-1
    • Remember: 50% of NF-1 cases are inherited
Neurological Disorders
  • Mild cognitive dysfunction
    • ADHD, Learning disabilities
  • Seizures
    • Seizures are more common in NF-1, especially in the setting of brain tumors (partial-onset seizures more common than generalized).
    • Mesial temporal sclerosis is also an identifiable contributing factor to seizures in NF-1.
References
  • Adil, Abdullah, and Achint K. Singh. “Neurofibromatosis Type 1 (Von Recklinghausen).” In StatPearls. Treasure Island (FL): StatPearls Publishing, 2018. http://www.ncbi.nlm.nih.gov/books/NBK459358/.
  • Banerjee, Sutapa, Nikkilina R. Crouse, Ryan J. Emnett, Scott M. Gianino, and David H. Gutmann. “Neurofibromatosis-1 Regulates MTOR-Mediated Astrocyte Growth and Glioma Formation in a TSC/Rheb-Independent Manner.” Proceedings of the National Academy of Sciences of the United States of America 108, no. 38 (September 20, 2011): 15996–1. https://doi.org/10.1073/pnas.1019012108.
  • Friedman, J. M. “Neurofibromatosis 1.” In GeneReviews®, edited by Margaret P. Adam, Holly H. Ardinger, Roberta A. Pagon, Stephanie E. Wallace, Lora JH Bean, Karen Stephens, and Anne Amemiya. Seattle (WA): University of Washington, Seattle, 1993. http://www.ncbi.nlm.nih.gov/books/NBK1109/.
  • Garrouche, Nada, Amel Ben Abdallah, Nadia Arifa, Ibtissem Hasni, Yasser Ben Cheikh, Waad Ben Farhat, Sana Ben Amor, and Hela Jemni. “Spectrum of Gastrointestinal Lesions of Neurofibromatosis Type 1: A Pictorial Review.” Insights into Imaging, September 4, 2018. https://doi.org/10.1007/s13244-018-0648-8.
  • “NF1 | Children’s Tumor Foundation.” Accessed September 20, 2018. http://www.ctf.org/understanding-nf/nf1.
Reference, Genetics Home. “Neurofibromatosis Type 1.” Genetics Home Reference. Accessed September 20, 2018. https://ghr.nlm.nih.gov/condition/neurofibromatosis-type-1.
Image References
  • Lisch nodule (pigmented iris nodule).
    • Photogragh from Dimitrios Malamos
  • Cafe au lait spot
    • Photogragh from Accrochoc
  • Malignant peripheral nerve sheath tumor of the lower extremity.
    • Image from Cases Journal
  • Cutaneous neurofibromas
    • Photograph from Klaus D. Peter

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