Tumours are common in adults with NF1; but they are usually benign growths, which means they are not a cancer or a malignancy, ie: they are localised to one spot and do not spread. The kinds of tumours seen in persons with NF1 include neurofibromas, plexiform neurofibromas, and astrocytomas. The biggest change that an adult with NF1 may notice is the gradual and continual development of new neurofibromas. Neurofibromas are benign tumours that develop on or under the skin along a nerve. They may look like small bumps or nodules. Even though they are called "tumours" , cutaneous or skin neurofibromas will almost never develop into cancer. Neurofibromas may often start developing during times of hormone changes, like adolescence and during pregnancy. Many women also note an increase in the growth of pre-existing tumours during pregnancy. This may be due to the increase in blood volume and blood flow that accompanies pregnancy, and there may be a decrease in the size or prominence of these neurofibromas once the baby is born.  Typically, adults with NF1 will acquire more tumours as they age.

Neurofibromas usually develop gradually over time and may continue to grow in size for a period of time. There is no way to determine how many neurofibromas a person with NF1 may develop, when they will start to develop, or where on the body they will grow. These factors vary from person to person. Some people with NF1 may have only one or two neurofibromas while others may develop several. They can grow anywhere there are nerves - on the face, the scalp, the chest, around the nipple, as well as inside the body. Approximately only one in five people with NF1 will have neurofibromas on the face. There is nothing a person can do to prevent the growth of neurofibromas. Things like certain foods, smoking, caffeine, and heat do not stimulate their growth.

Some people may elect to have a neurofibroma removed for cosmetic reasons, because it itches or stings, or because it is in a place where it is frequently irritated or catches on clothing. Neurofibromas should be removed by a doctor who has experience with NF1. They may be removed by surgery or occasionally by laser. If a neurofibroma is removed, it may or may not grow back. Occasionally, removal of a neurofibroma may cause a thickened scar.

Plexiform neurofibromas are another type of benign tumour that grows along nerves. Unlike the typical skin neurofibroma that grows as a small-defined nodule, the plexiform neurofibroma is a larger growth with less well-defined borders. It can feel like a bunch of cords or knots beneath the skin. Plexiform neurofibromas also differ from the discrete neurofibromas because they usually appear before adulthood. These tumours can be painful if hit or bumped. They also can be disfiguring depending on their size and location. Less commonly, a plexiform neurofibroma tumour can become cancerous. People with a plexiform neurofibroma should always let their doctors know immediately if they develop a new persistent pain or a change in their usual physical abilities and activity (weakness, numbness, change in bladder or bowel function). They also need to seek medical advice if the tumour grows rapidly, changes in shape or colour, or feels harder in texture.

An optic glioma is a tumour on the optic nerve inside the skull. The optic nerve functions to transmit vision to our brains. Because these tumours grow only in children, adults with NF1 do not need to worry about this type of tumour and the visual problems that can be associated with it. An optic glioma diagnosed during childhood rarely progresses during the adult years to cause problems. Individuals who notice a change in their eyesight should consult their ophthalmologists. The most common reason for deterioration in vision in adults result from changes in the eye lens associated with age. This is unrelated to NF1.

In rare instances a person with NF1 can develop a brain tumour called an astrocytoma. Adults with NF1 who experience persistent new headaches or a change in their usual physical abilities or activity (like weakness, numbness, or a change in personality or memory) should promptly notify their doctors. Further evaluation may be needed.

High blood pressure, also called hypertension, can be seen in persons with NF1. Thus, it is important that adults have their blood pressure monitored yearly by their doctors. Sometimes the high blood pressure is not specifically related to NF1, inasmuch as high blood pressure is common among people who don't have NF1. Regardless of the cause, high blood pressure is treatable. Rarely, individuals with NF1 can have high blood pressure caused by pheochromocytomas, tumours that are usually benign and secrete certain hormones. In these cases, blood pressure is high only on some occasions; and headaches, sweating, and palpitations may accompany the hypertension.

Pheochromocytomas can be treated with drugs and removed surgically.

Some adults complain of chronic pain. Back pain is sometimes related to neurofibromas involving the spine that are not easily removed with surgery. For the adult with severe and chronic pain that has been fully investigated, a referral to a doctor who specializes in pain management can sometimes be helpful in reducing the degree of pain experienced. Chronic pain from neurofibromas can often be alleviated by a combination of pain-relief medicines. Headaches can be a problem for some individuals, and migraine headaches are more common in NF1. Doctors specializing in neurology and/or pain management may have ideas to reduce the frequency and/or intensity of the headaches.

Although it is not understood why itching occurs, it is a frequent complaint of persons with NF1. Some people benefit from medications like antihistamines or topical corticosteroids that reduce the itching.

Women with NF1 may wonder about the effects of their NF1 on pregnancy as well as the effects of pregnancy on their NF1. The answers to these questions are not completely known. We do know that fertility is not reduced in women who have NF1 or in the wives of men with NF1. Anecdotal evidence suggests an increase in the number of neurofibromas with the use of birth control pills; however, this has not been proven to be true.

During pregnancy, about half of women report an increase in the number of neurofibromas and/or enlargement of already existing neurofibromas. Although there are no specific pregnancy concerns, women with NF1 tend to have a higher Caesarean section rate than women without NF1; but women with NF1 usually have regular deliveries that do not require a Caesarean section.

Some doctors originally reported problems with high blood pressure and preterm labour in pregnant women with NF1; however, more recent studies have not found such correlations. Regardless, women should let their obstetricians know that they have NF1 and also inform their NF1 doctors when they become pregnant.

When the man or woman in a couple has NF1, the decision about whether or not to have children can sometimes be a difficult one and must be decided by the couple themselves based upon what the couple thinks will be best for their family. What one couple decides may not be what is best for another couple and family. We know that when someone with NF1 has children, each child will have a 50-50 chance of having NF1. Someone's personal experience with NF1 may also affect his or her decision about having children. It is important to remember that, because NF1 is so variable from person to person, a child may or may not have the same medical problems as his or her parent. Talking with a genetic counsellor before conception is recommended to help persons with NF1 better understand the chances of having a child born with NF1, the spectrum of medical concerns associated with NF1, and genetic testing, as well as alternatives such as adoption and artificial insemination, and preimplantation genetic diagnosis. Genetic counsellors also help by providing additional information, but they will not tell a couple what they should do. Prenatal diagnosis by genetic testing is now available. It is generally used when one of the parents has NF1 and there is a 50% risk of having a child with NF1 in each pregnancy. The risks of unaffected parents who have a child with NF1 of having a second child with NF1 are very low (less then 1%), and prenatal diagnosis is usually not recommended.

When a couple  have children, and one of the parents has NF1, each child should be evaluated for features of NF1 by a doctor specializing in NF1 in the first few months after birth to look for signs of NF1, such as cafe-au-lait spots. If the child is thought to be affected they will be monitored.

Most adults with NF1 will have Lisch nodules. These are the small raised nodules that develop on the coloured part of the eye (the iris) as someone ages. Lisch nodules do not affect vision and do not cause any problems but simply serve as a feature helpful in diagnosing NF1.

Some persons with NF1 may have been diagnosed with a learning disorder as a child. These learning disabilities are not progressive and will not worsen over time as an adult. Some adults find difficulty with reading, writing, concentration, coordination and finding their way around. They may experience problems in filling in application forms for jobs or for social services. Individuals should consult their doctors, for adult literacy programs and support networks are available to help with these difficulties.

Some adults with NF1 may have had speech problems in childhood which may continue in adulthood. There is no evidence that speech problems are progressive in adulthood, and they are usually mild. Individuals may have difficulty in adjusting the rate, volume and pitch (tone) of their speech, and sometimes their speech has a nasal quality.

Evaluation by a speech pathologist is useful in this situation to determine if therapy will be useful.

Epilepsy (seizures) is seen a little more frequently in people with NF1 than in people who do not have NF1. The seizures are usually easily controlled by drugs. Individuals with this complication should consult a neurologist for advice and treatment.

Physical Appearance: Some adults worry about becoming disfigured as a result of their NF1. Although most adults will develop neurofibromas on their skin, severe disfigurement is not common. NF1 is not the same as "Elephant Man's disease", which is a rare and entirely separate condition. Curvature of the spine, called scoliosis, can be seen in growing children, but it is not a feature that starts in adulthood. A scoliosis diagnosed in childhood will persist in adulthood and can occasionally cause some problems.

Plexiform neurofibromas can sometimes be disfiguring depending upon their size and where on the body they are located. Some people with NF1 may be embarrassed by the appearance of the neurofibromas on their skin; and they may be especially self-conscious with regard to the opposite sex. Sometimes it helps to talk about one's feelings about NF1 with friends, family, others who have NF1, or a professional counsellor.

It is recommended that adults with NF1 have evaluations once a year by a doctor who knows about NF1. The doctor will check blood pressure and perform a detailed physical and neurologic exam. MRI exams are not part of the usual recommendations unless there is a specific concern or problem. Brain MRIs in persons without medical problems are often normal. They may show UBOs (unidentified bright objects). UBOs are bright spots on the MRI that are often seen in persons with NF1. They are of no clinical significance, do not correlate with other medical problems or cancer, and generally do not require any follow-up.

People with NF1 can donate their blood and organs to other people who are in need of blood or an organ transplant. The person who receives their blood and/or organs will not develop NF1 as a result of the blood/organ donation.