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Neurofibromatosis type 1
NF1 is a relatively common inherited condition, typically presenting with distinctive skin findings in early childhood. It can lead to a range of health issues, including nerve tumours, bone abnormalities, and an increased risk of certain cancers, affecting individuals differently.
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Overview
Neurofibromatosis type 1 (NF1) is a lifelong genetic condition that causes tumours to grow on nerve pathways throughout the body. While most of these tumours are benign (non-cancerous), they can sometimes cause health problems depending on their size and location. NF1 affects approximately 1 in 3,000 people globally and is one of the more common inherited conditions [PMID:33678096].
The condition can affect many different parts of the body, including the skin, eyes, bones, and the nervous system. The signs and symptoms of NF1 vary widely among individuals, even within the same family. While some people may have mild features, others can experience more significant health complications. Understanding these potential effects is important for long-term management and care.
Symptoms & clinical features
The symptoms of NF1 typically become apparent during childhood, often starting with skin changes. A common feature is the presence of 'café au lait' spots, which are flat, light brown patches on the skin. Six or more of these spots, particularly if they are larger than 0.5 cm in young children or 1.5 cm in adolescents and adults, are a key diagnostic sign [PMID:33678096]. Another common skin finding is axillary (armpit) or inguinal (groin) freckling, which are small, numerous freckles in skin folds.
Over time, neurofibromas may develop. These are benign tumours that grow on or under the skin, or on nerves deeper within the body. They vary in size and number. Other potential symptoms include Lisch nodules, which are harmless, tiny brown spots on the iris of the eye, and bone abnormalities such as bowing of the legs or scoliosis (curvature of the spine). Some individuals with NF1 may also experience learning difficulties or attention deficit hyperactivity disorder (ADHD) [PMID:33678096]. In rare cases, more complex tumours, including optic pathway gliomas (tumours affecting the nerves to the eye), can develop. The specific combination and severity of symptoms are unique to each person with NF1.
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Affected organs
NF1 primarily affects organs and systems derived from the neural crest during development, leading to widespread impact. The skin is commonly affected, showing café au lait spots and freckling, and developing cutaneous and plexiform neurofibromas. The nervous system is also significantly involved, with neurofibromas growing on nerves. These can range from small, benign skin lesions to larger, more complex tumours that may affect nerve function.
Bone development can be altered, leading to conditions like scoliosis, bowing of long bones, or pseudarthrosis (a 'false joint' due to a non-healing fracture). The eyes may show Lisch nodules on the iris, and in some cases, optic pathway gliomas can affect vision. Other systems, including the cardiovascular system (with a slightly increased risk of blood vessel abnormalities) and the endocrine system, can also be affected, though less commonly.
Risks & severity
The severity of NF1 can vary considerably, even within the same family, making it difficult to predict how an individual will be affected. While many people with NF1 lead full lives with mild symptoms, others may experience more significant health challenges. A key aspect of NF1 is an increased lifetime risk of developing certain tumours. This includes the neurofibromas themselves, which are typically benign but can sometimes cause problems due to their size or location, or rarely, transform into malignant peripheral nerve sheath tumours (MPNSTs), a type of cancer [PMID:35787680].
Individuals with NF1 also have an increased risk of developing other cancers, including certain brain tumours, leukaemia, and breast cancer at a younger age. Regular monitoring and surveillance are therefore important for early detection and management of potential complications. The age of onset for symptoms varies; skin signs often appear in infancy or early childhood, while other complications like neurofibromas or bone issues may develop later. Learning difficulties are common in childhood.
Genetic causes
Neurofibromatosis type 1 is caused by pathogenic variants in the NF1 gene. This gene is located on chromosome 17 and provides instructions for making a protein called neurofibromin. Neurofibromin plays a crucial role in regulating cell growth and division, acting as a 'molecular brake' to prevent cells from growing too quickly or uncontrollably.
When a pathogenic variant occurs in the NF1 gene, it leads to a faulty or absent neurofibromin protein. This disruption means the 'brake' on cell growth is less effective, which allows cells to divide more freely. This uncontrolled cell growth is what leads to the formation of neurofibromas and the other characteristic features of NF1. Research suggests that a wide variety of different changes in the NF1 gene can lead to the condition [PMID:35787680].
- NF1 neurofibromin 1The NF1 gene encodes neurofibromin, a tumour suppressor protein that controls cell growth by regulating signalling pathways critical for preventing uncontrolled cell division.
Inheritance pattern
NF1 is inherited in an autosomal dominant pattern. This means that a person only needs to inherit one copy of the altered NF1 gene to develop the condition. If a parent has NF1, there is a 50% chance with each pregnancy that their child will also inherit the condition.
About half of all people with NF1 inherit the altered gene from a parent who also has the condition. In the other half of cases, NF1 results from a new genetic change (a 'de novo' mutation) in the NF1 gene that occurred during the formation of the egg or sperm, or in early embryonic development. In these situations, the parents do not have NF1, and the chance of having another child with NF1 is generally very low, though genetic counselling is recommended to discuss specific risks.
Each child has a 50% chance of inheriting the pathogenic variant, regardless of sex.
Diagnosis & testing
Diagnosis of NF1 is primarily based on a combination of clinical features and, in many cases, confirmed by genetic testing. A clinical diagnosis is usually made when an individual meets at least two specific diagnostic criteria, such as the presence of multiple café au lait spots, axillary or inguinal freckling, two or more neurofibromas, Lisch nodules, certain bone abnormalities, or a family history of NF1. These criteria are well-established and used by healthcare professionals globally.
Genetic testing for pathogenic variants in the NF1 gene can confirm a diagnosis, especially in cases where clinical features are unclear or when testing is performed in children at risk. Referral for genetic testing is typically made by a clinical geneticist or another specialist following an initial assessment. In the UK, genetic testing for NF1 is available through the NHS Genomic Medicine Service (GMS) and is supported by specific R-codes (e.g., R156 Neurofibromatosis type 1 - diagnosis). This testing can identify the specific genetic change causing the condition, which can be helpful for family planning and understanding the inheritance pattern.
Management & lifestyle
Management of NF1 focuses on monitoring for potential complications and addressing symptoms as they arise, within the framework of NHS care pathways. There is no cure for NF1, but multidisciplinary care helps to manage its various manifestations. Regular clinical reviews, often involving specialists in genetics, neurology, dermatology, ophthalmology, and orthopaedics, are recommended. These appointments typically include monitoring for growth and development, blood pressure checks, skin examinations, and eye examinations to detect Lisch nodules or optic pathway gliomas.
Surgery may be an option for neurofibromas that are causing pain, disfigurement, or compressing nerves or organs. For plexiform neurofibromas that cannot be surgically removed, specific medications, such as selumetinib, have shown promise in reducing their size and associated symptoms in some paediatric patients. Learning difficulties and ADHD may be managed with educational support and appropriate therapies. The NHS Genomic Medicine Service provides pathways for ongoing clinical care and surveillance, ensuring individuals receive personalised management plans to optimise their health and quality of life.
UK care pathway
In the UK, individuals suspected of having NF1 are typically referred to a Clinical Genetics service for assessment and diagnosis. This pathway ensures access to specialist genetic counselling, which is crucial for understanding the condition, its inheritance, and implications for family members. Diagnosis can be confirmed through genetic testing available via the NHS Genomic Medicine Service, using specific R-codes like R156. Following diagnosis, care is managed through a multidisciplinary approach, often involving a geneticist, neurologist, dermatologist, and other specialists, depending on the individual's specific symptoms and needs. Regular follow-up appointments and surveillance are key components of this care.
Frequently asked questions
What is the main difference between Neurofibromatosis type 1 and type 2?
Neurofibromatosis type 1 (NF1) and type 2 (NF2) are distinct genetic conditions. NF1 mainly causes skin changes, neurofibromas on nerves, and bone issues. NF2 primarily causes tumours on the nerves leading to the ears (vestibular schwannomas) and can lead to hearing loss, with fewer skin symptoms than NF1. They are caused by changes in different genes (NF1 and NF2, respectively).
Are the lumps associated with NF1 always cancerous?
No, the lumps, called neurofibromas, associated with NF1 are typically benign (non-cancerous). However, in a small percentage of cases, these benign tumours can transform into a type of cancer called a malignant peripheral nerve sheath tumour (MPNST). Regular monitoring is important to detect any changes.
Can NF1 affect learning and development in children?
Yes, NF1 can affect learning and development. Some children with NF1 may experience learning difficulties, including challenges with reading, writing, or mathematics. Attention deficit hyperactivity disorder (ADHD) is also more common in children with NF1. Educational support and specialist assessments can help manage these challenges.
If I have NF1, will my children definitely inherit it?
NF1 is inherited in an autosomal dominant pattern. This means if you have NF1, there is a 50% chance with each pregnancy that your child will inherit the altered NF1 gene and develop the condition. This inheritance pattern applies equally to sons and daughters.
Is there a cure for Neurofibromatosis type 1?
Currently, there is no cure for NF1. However, management focuses on monitoring for potential complications and treating symptoms as they arise. This often involves a team of specialists providing multidisciplinary care, including surveillance, surgical interventions for problematic tumours, and sometimes targeted medication for specific types of neurofibromas.
References
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- Sato AA, Earl D, Wallace SE. Targeted Therapies in Neurofibromatosis Type 1. American journal of medical genetics. Part C, Seminars in medical genetics. 2025. PMID: 40968507
- Mançano AD. Neurofibromatosis type 1. Radiologia brasileira. 2022. PMID: 35210668
- McLaughlin ME, Jacks T. Neurofibromatosis type 1. Methods in molecular biology (Clifton, N.J.). 2003. PMID: 12710690
- Colman SD, Wallace MR. Neurofibromatosis type 1. European journal of cancer (Oxford, England : 1990). 1994. PMID: 7734210
- Ozarslan B, Russo T, Argenziano G. Cutaneous Findings in Neurofibromatosis Type 1. Cancers. 2021. PMID: 33530415
- Kinori M, Hodgson N, Zeid JL. Ophthalmic manifestations in neurofibromatosis type 1. Survey of ophthalmology. 2018. PMID: 29080631
- Mansilla-Polo M. Neurofibromatosis type 1. Medicina clinica. 2025. PMID: 38937219