Understanding Possible Explanations for Isolated Features of NF

Frequently I receive questions, through both e-mails and individuals who are referred to my office, regarding patients who have one isolated feature of NF but do not have a confirmed diagnosis of neurofibromatosis. These isolated features most often occur in the form of either plexiform neurofibromas or optic gliomas, although they sometimes may include dermal neurofibromas or bone dysplasia.  It is important to know that isolated features of NF can occasionally been seen in both children and adults who do not actually have the condition.  I’d like to give a brief overview of how we evaluate patients with only one isolated feature of NF in the absence of other symptoms and provide some possible explanations of why this phenomenon may occur.

Some individuals develop plexiform neurofibromas – tumors that involve multiple branches of large nerves – in one isolated area of the body, such as the spine, with no other features of NF. The age of presentation varies, but it usually begins from the teenage years into adulthood, as the symptoms of a plexiform neurofibroma do not become apparent until adolescence.  Isolated optic gliomas, tumors of the optic nerve, can also occur in children and adults who have no other features of NF. Unlike isolated plexiform neurofibromas, optic gliomas that occur in individuals who do not have NF are typically more aggressive tumors than those found in people who have neurofibromatosis.  Some individuals also develop isolated dermal neurofibromas or bone dysplasia in the absence of other NF features and with no confirmed diagnosis of neurofibromatosis.

When we see someone in our clinic with an isolated feature of NF, we provide a comprehensive evaluation to make certain that subtle features of the condition are not present. In some cases, if possible, we obtain a tissue sample of the tumor, although this is often difficult due to the location of tumors, such as plexiform neurofibromas deep inside the body.  Sometimes we obtain a blood sample for genetic testing; however, a negative result does not necessarily confirm that an individual does not have NF. 

There are at least three possible explanations for the occurrence of isolated NF features in some individuals.  The first is mosaicism, caused by a mutation in the NF1 gene that occurs early in embryonic development and that only affects certain cells in the body.  As a result,  individuals with mosaicism have features of NF1 that are limited to only one part of their body, such as neurofibromas or café-au-lait spots in a certain region. The only method of confirming mosaicism is to biopsy the lesion and do genetic testing on the tissue.  A second possible explanation for the occurrence of isolated features of NF is that there could be other, still unknown mechanisms that cause tumors that occur in people with NF to also occur in individuals who do not have the condition. 

A third possible explanation is related to the specific “two-hit” genetic mechanism that causes the development of tumors in people with NF1.  All persons have two copies of the gene, one inherited from each parent.  In individuals with NF1, one copy of the NF1 gene is altered, or mutated, due to either inheriting the mutated gene from a parent, a new mutation that occurs in the egg or sperm prior to conception, or from a mutation that occurs early in embryonic development.  This represents the “first-hit” genetic mutation.  For a neurofibroma to develop in someone with NF1, a random genetic mutation must occur to the other copy of the NF1 gene in the tissue that will become the neurofibroma, café-au-lait spot, or other lesion; this is referred to as the “second-hit” mutation.  Although an extremely rare occurrence, it is also possible for some individuals to acquire two random NF mutations, affecting each inherited copy of the NF1 gene, in a cell that could become a neurofibroma or other lesion.  This two-hit mutation – similar to lightning striking twice in the same place – could result in the development of an isolated feature of NF in the absence of other signs of the condition.

On another topic, there are two things to report regarding the UAB NF Program.  First, Dr. Ashley Cannon has joined the program as genetic counselor and clinical research coordinator.  Dr. Cannon has unique training both as a neuroscientist and genetic counselor; she will be seeing patients with me in clinic and also involved in many of our research studies and clinical trials.  Second, we will be hosting our annual NF Symposium this summer on Saturday, August 29.  As in the past, the focus will be on educating patients and families about NF and highlighting research progress.  We have assembled a group of speakers both from UAB and from the Children’s Tumor Foundation who will participate.  If interested in knowing more about the symposium please contact Dr. Cannon at acannon@uab.edu. We look forward to seeing as many families as possible at this event!

Responding to E-mailed Questions from Patients and Reviewing Diagnostic Criteria for Café-Au-Lait Spots and Groin Freckling

On an almost daily basis, I receive e-mails from people in all parts of the U.S. and other countries asking clinical questions about NF.  Most of the time, individuals who e-mail me have run across my name on social networking sites, such as a discussion board or a chat room devoted to the topic of NF.  There is a robust network of NF-related discussion forums on the Internet, and they can serve as a valuable resource for patients and families in locating specialists who can provide a definitive diagnosis and treatment plan. In this blog, I’d like to address the general principles I follow in replying to patients’ questions via e-mail. 

Because most of the people who contact me have questions about clinical features that might indicate NF – or they have already received a diagnosis and need a plan of treatment – my primary goal is to connect them with a qualified specialist in their area whenever possible, and I always stress in my response the importance of identifying a trusted clinician in the region.  Fortunately, specialists can be found relatively easily in most major U.S. cities.  For patients and families seeking assistance in locating a specialist, the Children’s Tumor Foundation (www.ctf.org) web site features a patient information tab that provides a list of specialists within the U.S.

However, finding a qualified NF specialist often can be challenging, especially for people in other countries.  In many regions of the U.S., and in many other countries, there is not ready access to NF specialists, and some physicians with the clinical knowledge to make an NF diagnosis may lack experience in managing complications and developing a treatment plan.  For these reasons, NF-related discussion boards and chat rooms have proven to be a valuable resource for patients and families seeking information and guidance.

Because I understand the importance of helping people gain access to accurate information about NF, I’m always glad to respond to any e-mailed questions I receive and consider it a privilege to communicate with patients who have NF-related concerns. However, I can’t provide specific medical advice to people whom I have not personally examined and whose records I have not reviewed.  Many people who e-mail me often attach photos, for example of café-au-lait spots, usually taken with a cell phone. Most of these photos are difficult to interpret, and it’s important not to give advice based on the limited information provided in an e-mail or photo. Instead, I focus on providing general information about NF that is not specific to their situation – perhaps about the value of genetic testing or a review of different treatment approaches.

Regarding the numerous e-mailed questions I receive asking if a child with café-au-lait spots has NF, the majority describe children in whom a diagnosis of NF is not obvious.  Parents of these children are usually distraught about the possibility of NF based on the presence café-au-lait spots, which may have been noticed by a pediatrician or other clinician.  Frequently, I have the impression that most are healthy children with a few spots that don’t fulfill the diagnostic criteria requiring six or more café-au-lait spots.  It is important to note that the vast majority of people with NF1 have this number of café-au-lait spots or more.  Sometimes, infants can develop café-au-lait spots, but café-au-lait spots usually begin to appear in the first few weeks of life.  By two years of age, a child with NF will have at least six café-au-lait spots, if they ever will.  It’s important to note that a young child with six or more café-au-lait spots that are clear usually will have NF1 that can be confirmed with genetic testing.  In my clinical experience, many children with between one and three spots usually don’t have NF.

There are some people with variant forms of NF who have fewer than six café-au-lait spots.  Some of these individuals develop internal neurofibromas, but have few visible on the skin.  Legius Syndrome is another condition that causes café-au-lait spots, although these individuals do not develop tumors; this is a benign condition that is much more rare than NF1, and genetic testing is required to confirm it.  Also, there are other conditions that can produce café-au-lait spots, though most are rare.  It should also be noted that some healthy people can have up to six spots with no other symptoms.

Freckling in the groin and under the arms is another feature used to confirm an NF1 diagnosis. While some parents may worry based on the presence of a few small freckles in these regions, it’s important to note that NF-related freckling appears between three and five years of age.  Instead of a few tiny freckles in these regions, there are usually many freckles in the region, as if paint were spattered from a paint brush.  Also, a café-au-lait spot that happens to appear under the arm or in the groin does not count as a skin fold freckle.

Because NF-related features such as café-au-lait spots and groin and underarm freckling are sometimes over-interpreted and often a source of unnecessary anxiety, it’s important to identify an experienced clinician who can make a recommendation about diagnosis and the use of genetic testing for NF based on the presence of specific clinical criteria. My continued objective in responding to e-mailed questions is to provide patients with accurate information about NF and assist them in identifying an experienced, trusted clinician who can provide additional information and guidance.

Measurement Technique for Dermal Neurofibromas Validated at UAB Expands Possibilities for Clinical Trials

In continuing our discussion from the previous blog regarding how the focus of a clinical trial is determined, I’d like to address the treatment and research of two distinctive features of NF that are of significant concern to patients – dermal neurofibromas and plexiform neurofibromas.  A frequent question from patients related to neurofibromas is:  Why do clinical trials focus on plexiform neurofibromas, while there are no clinical trials in progress for dermal neurofibromas? Many patients feel that dermal neurofibromas are an underappreciated feature of NF.  

The basis for focusing on plexiform neurofibromas thus far in clinical trials centers on three issues: first, complications of plexiforms are often more serious than for dermal neurofibromas and can sometimes be life-threatening; second, the several mouse models for testing drug effectiveness in plexiform neurofibromas are better established than the model currently available for dermal neurofibromas; and the technology for measuring dermal neurofibromas is not as advanced as for plexiforms, making it more difficult to determine the effectiveness of a specific drug on tumor growth.  The good news is that the UAB NF Program has worked with collaborators recently to establish the validity of a measurement technique for dermal neurofibromas, and this method will enable the development of future clinical trials focused on testing the effectiveness of drugs in slowing or reversing the growth of these types of tumors.

In providing a more thorough explanation about the future of clinical trials for dermal neurofibromas, it’s first helpful to understand the significant differences between dermal and plexiform neurofibromas.  Dermal neurofibromas are soft, benign tumors that develop under the skin.  These tumors typically appear after puberty and grow slowly over a period of time. While they are variable in size and number, dermal neurofibromas can be disfiguring in some patients, causing embarrassment and problems with self-esteem.  In fact, the unpredictability of dermal neurofibromas can be the most daunting aspect of this NF feature; some individuals have few or none, while others’ bodies may be completely covered.   Many women with NF1 experience increased growth of neurofibromas during pregnancy, suggesting that hormonal changes may be related to their development. 

The treatment approach for dermal neurofibromas is dependent on the number and location of tumors, although the most common approach is to leave them alone due to their benign nature and the low risk of medical problems. The most common treatment is surgical removal of individual tumors using either conventional plastic surgery, laser treatment, or a procedure called electrodessication that uses an electrical current to remove a large number of tumors at one time.   While these treatments can be effective, each can leave scarring and none of the options prevents additional tumor development.  

Plexiform neurofibromas are congenital tumors that often first appear in infancy or early childhood as a soft swelling under the skin.  Affecting about 50% of people with NF1, these tumors are frequently larger and usually involve multiple branches of large nerves.  Depending on their location, plexiform neurofibromas can lead to abnormal bone growth or pressure on nerves, blood vessels, or organs. For example, plexiform neurofibromas along the spine can compress the spinal cord, leading to weakness, pain, and sometimes paralysis.  Surgical removal can reduce the overall size of the tumor, although it will not stop the tumor from growing.

Because the symptoms of plexiforms can be urgent and potentially life-threatening, this feature has been given greater priority over dermal neurofibromas in clinical trials.  Plexiform and dermal neurofibromas are similar at the cellular level, however, so the hope is that some treatments for plexiforms may also be effective for dermal neurofibromas.

Until recently, the challenge in testing the effectiveness of specific drugs for the treatment of dermal neurofibromas has centered on the difficulty of obtaining accurate measurements of these tumors. Unlike plexiforms that grow quickly and can be measured relatively easily with imaging studies, the slower growth rate and configuration of dermal neurofibromas make them difficult to measure accurately.

In collaboration with a research group in Brazil, scientists in the UAB NF Program have tested a measurement method over the past several years that recently has been validated as providing an accurate estimate of dermal neurofibromas (Publication). Using adhesive paper frames with a 10 cm x 10 cm window cut-out, a group of patients’ dermal tumors were documented and measured by attaching the paper frame to a specific region identified by a physical landmark that was photographed; this procedure allowed us to measure growth of dermal neurofibromas over a period of time.

This recently validated measurement technique for dermal neurofibromas has opened the door to conducting clinical trials focused on testing medications to treat this feature that is problematic for so many NF patients.  We are now exploring the possibility of conducting a small, independent pilot trial to determine the effectiveness of a treatment for dermal neurofibromas.  Also, we have plans to design a secondary arm of a clinical trial for plexiform neurofibromas that would test the effectiveness of the medication on dermal neurofibromas.  As a secondary endpoint within this trial, individuals with plexiform neurofibromas would undergo measurements of dermal neurofibromas over a period of time to determine if the medication has had an effect on slowing the growth.

We still do not know when there will be effective treatments for the various aspects of neurofibromatosis.  Those with dermal neurofibromas should know that this aspect of the condition is not being ignored, and I am hopeful that clinical trials for dermal tumors will become a reality soon.