Teebi-Shaltout syndrome is a very rare genetic condition that is present from birth. It mainly affects physical development and is often recognized in infancy or childhood because of distinctive facial features and other body signs. Not everyone will have the same experience, but early signs of Teebi-Shaltout syndrome can include differences in head, face, and sometimes the hands or feet. Teebi-Shaltout syndrome is lifelong, and care usually focuses on supportive treatment, regular checkups, and help from specialists based on a child’s needs. Because it is rare, the outlook can vary, and doctors often tailor care to the specific features each person has.
How many people live with Teebi-shaltout syndrome?
There is no trustworthy published estimate of how many people live with Teebi-Shaltout syndrome worldwide or in the United States. It appears to be extremely rare, but the number of people living with it is currently unknown.
Overview
Teebi-shaltout syndromeSymptoms
Teebi-Shaltout syndrome mainly affects facial development. Common features include widely spaced eyes, a broad nose, unusual eyebrow shape, and sometimes cleft lip or palate; some children also have hearing loss or heart differences.
Outlook and prognosis
Teebi-Shaltout syndrome is very rare, so outlook varies. Many affected children grow into adulthood, with day-to-day needs shaped mainly by differences in facial features, speech, learning, or hearing when these are present.
Causes and risk factors
Teebi-Shaltout syndrome is usually caused by a gene change present from conception, often arising new or inherited in an autosomal dominant pattern. Most people have no lifestyle or environmental cause, though these factors can affect overall health and related complications.
Genetic influences
Genetics are central to Teebi-Shaltout syndrome, which is linked to a disease-causing gene change. Genetic testing can help confirm Teebi-Shaltout syndrome and guide family counseling about recurrence risk in future pregnancies.
Diagnosis
Teebi-Shaltout syndrome is usually diagnosed from clinical features seen on exam, often supported by imaging findings. The genetic diagnosis of Teebi-Shaltout syndrome may be confirmed with genetic tests. A genetics specialist often guides this process.
Treatment and drugs
Treatment for Teebi-shaltout syndrome focuses on each person's needs. Many need regular checks for growth, development, hearing, vision, and heart problems. Supportive care can include early therapies, special education, and treatment of any birth differences.
Symptoms
Teebi-Shaltout syndrome usually shows up as a pattern of physical traits that are often noticeable from birth or early childhood, especially in the face and head. For many people with Teebi-Shaltout syndrome, some of the early features of Teebi-Shaltout syndrome include widely spaced eyes, a broad forehead, and differences in the nose or mouth. Not everyone has the same signs, and some differences are mild. Day to day, this can mean extra support with feeding, speech, hearing, or dental care, depending on which features are present.
Many people with Teebi-Shaltout syndrome have eyes that sit farther apart than usual. This mainly affects facial appearance, though some may also need checks for vision or eye alignment problems.
A broad or prominent forehead can be part of the pattern. The hairline and eyebrows may also look distinctive, which often helps doctors recognize the syndrome.
The nose may look broad or differently shaped, and the area between the nose and upper lip can appear longer or flatter. Some people also have a thin upper lip or other mild differences around the mouth.
Some people have a high roof of the mouth or a cleft lip or palate. In daily routines, this might show up as small but noticeable changes in feeding, speech, or dental care needs.
How people usually first notice Teebi-shaltout syndrome?
Teebi-Shaltout syndrome is usually first noticed very early in life, often at birth or during infancy, when doctors or family members see a pattern of distinctive facial features rather than a single warning sign. The first signs of Teebi-Shaltout syndrome may include widely spaced eyes and other recognizable differences in the shape of the forehead, nose, or other facial features, sometimes followed by concerns at early checkups about growth or development. Because this is a rare genetic condition, how Teebi-Shaltout syndrome is first noticed can vary from child to child, and the diagnosis is usually confirmed only after a clinician recognizes the overall pattern.
Types of Teebi-shaltout syndrome
No distinct types of Teebi-shaltout syndrome are widely recognized.
Can I slow down the onset of symptoms?
No, there is no good evidence that lifestyle changes or medical treatment can meaningfully delay the start of symptoms in Teebi-Shaltout syndrome, because it is a very rare genetic condition and signs often begin very early in life. There are also no proven preventive medicines for it, but regular follow-up with a care team can help find problems early and start supportive care sooner, which may improve daily life even though it does not prevent the condition. While this can feel frustrating, early support and careful monitoring can still make a real difference in how well someone lives with the condition.
What genetics can tell you about symptoms
In Teebi-Shaltout syndrome, genetics can help confirm the diagnosis, but because the condition is very rare, they usually cannot predict with much certainty exactly which symptoms someone will have, how severe they will be, or when they will start. The small number of reported cases suggests there can be real differences from one person to another, even among people thought to have the same underlying genetic cause. In practice, the genetic result is most useful as one part of the picture, alongside a child’s growth, development, and physical features over time.
Causes and risk factors
The main cause of Teebi-Shaltout syndrome is an inherited or new gene change that affects early development before birth. The biggest biological risk factor is family history, because a parent with the same gene change can pass it on. Many children with Teebi-Shaltout syndrome are the first in their family to have it, which means the change happened for the first time in them. Lifestyle, diet, and common environmental exposures are not known to cause Teebi-Shaltout syndrome, though they still matter for overall health. Genetic testing for Teebi-Shaltout syndrome can sometimes clarify your personal risk.
What are the most common causes or risk factors?
Teebi-Shaltout syndrome is a rare genetic condition that is usually caused by a change in a gene called SPECC1L, which helps guide how a baby develops before birth. The main risk factor is family history, since an affected parent can pass the condition on, although the gene change can also happen for the first time in a child with no family history. There are no well-established lifestyle, diet, or environmental causes.
Environmental and biological risk factors
When people look for risk factors for Teebi-shaltout syndrome, the honest answer is that very few have been identified. Awareness of both biological and environmental influences helps you feel prepared. So far, published reports have not shown clear links with common maternal illnesses, routine pregnancy events, or outside exposures.
No specific medicine, infection, radiation, heavy metal, or chemical exposure has been proven to raise the chance of Teebi-shaltout syndrome. At this time, there is no established environmental trigger doctors can point to.
No common maternal health condition has been consistently linked with Teebi-shaltout syndrome. In reported cases, a clear body-based risk during pregnancy has not been identified.
Problems such as prematurity, low birth weight, or delivery complications are not known to cause this syndrome. These events can affect a baby's health in other ways, but they are not established risk factors here.
Teebi-shaltout syndrome is extremely rare, so research studies are small. That means subtle biological or environmental influences can be hard to confirm, and current guidance is based on the fact that no clear non-inherited risk factors are known.
Genetic risk factors
For many living with Teebi-Shaltout syndrome, the cause lies in a change in a gene that helps facial tissues develop before birth. The genetic causes of Teebi-Shaltout syndrome most often involve the SPECC1L gene. Some risk factors are inherited through our genes. In some families the change is passed down, while in others it happens for the first time in the child.
SPECC1L changes: Most reported cases of Teebi-Shaltout syndrome are linked to a harmful change in the SPECC1L gene. This gene helps guide how parts of the face and head grow and come together during early development.
New variant: In some children, the genetic change is new and was not inherited from either parent. This is called a de novo change, and it means the syndrome can appear in a family with no earlier history.
Dominant inheritance: When a parent carries the SPECC1L change, it can be passed to a child in an autosomal dominant pattern. In practical terms, each pregnancy has a 1 in 2, or 50%, chance of inheriting the altered gene.
Family history: A family history of Teebi-Shaltout syndrome or a known SPECC1L change raises the chance that the condition runs in the family. Sometimes a parent has milder features, so the inherited pattern is only noticed after a child is diagnosed.
Lifestyle risk factors
Lifestyle habits do not cause Teebi-Shaltout syndrome, because it is a genetic condition. However, how lifestyle affects Teebi-Shaltout syndrome can be important, especially when the syndrome includes craniofacial differences, feeding problems, hearing or vision issues, developmental delay, or low muscle tone. Daily routines can either reduce strain on these affected body systems or make symptoms and complications harder to manage.
Poor calorie intake, limited food variety, or difficult feeding routines can worsen poor growth and low energy in a child with Teebi-Shaltout syndrome. Structured meals, texture changes when needed, and attention to swallowing or chewing problems may support growth and day-to-day functioning.
Too little movement can increase deconditioning, stiffness, and delayed motor progress when Teebi-Shaltout syndrome affects muscle tone or coordination. Safe, regular activity and therapist-guided exercise may help balance, endurance, and independence.
Irregular sleep schedules or untreated sleep disruption can worsen irritability, attention, learning, and daytime fatigue in people already coping with developmental or craniofacial challenges. Good sleep routines and prompt assessment of snoring or breathing pauses may reduce added functional strain.
Inconsistent use of hearing aids or poor communication routines can magnify speech and language delays if hearing loss is part of Teebi-Shaltout syndrome. Consistent device use, quiet listening environments, and speech-focused interaction can improve communication outcomes.
Risk prevention
Teebi-Shaltout syndrome is a rare genetic condition, so there is no known way to prevent the syndrome itself once the gene change is present. For families, prevention usually means lowering the chance of passing it on through genetic counseling and, when possible, genetic testing before or during pregnancy. For people living with Teebi-Shaltout syndrome, prevention is mostly about reducing complications, supporting development, and catching problems early.
If Teebi-Shaltout syndrome is suspected in a family, meeting with a genetics specialist can help clarify inheritance and recurrence risk. This can guide decisions before pregnancy or early in pregnancy.
When the genetic cause of Teebi-Shaltout syndrome is known in one family member, targeted testing may help identify other relatives who could carry the same change. Knowing your risks can guide which preventive steps matter most.
Some families may choose prenatal testing or IVF with embryo testing if the disease-causing variant has been identified. These options do not treat Teebi-Shaltout syndrome, but they may reduce the chance of having an affected child.
For many living with Teebi-Shaltout syndrome, routine visits with the right specialists can help spot new concerns before they become bigger problems. This often matters more than trying to prevent early symptoms of Teebi-Shaltout syndrome at home without guidance.
Can you prevent Teebi-shaltout syndrome?
No, Teebi-Shaltout syndrome usually cannot be prevented. It is a rare condition caused by a change in genes, so there are no proven lifestyle steps, medicines, or habits that can stop it from happening. If it has affected your family, speaking with a genetics specialist before pregnancy may help you understand the chance of it happening again, but it cannot guarantee prevention.
Transmission
Teebi-Shaltout syndrome is not infectious, so it cannot be passed from one person to another through touching, coughing, kissing, sex, or sharing food at home, school, or work. Instead, it is a rare genetic condition that is present from conception. The genetic transmission of Teebi-Shaltout syndrome involves a change in genetic material that may be inherited in some families or may happen for the first time in a child. Because Teebi-Shaltout syndrome is very rare, a genetics specialist is often the best person to explain how Teebi-Shaltout syndrome is inherited in your family and what that may mean for future pregnancies.
When to test your genes
For Teebi-Shaltout syndrome, genetic testing is usually considered when a child has a recognizable pattern of congenital features, growth or developmental differences, or a family history suggesting the condition. Testing is not routine population screening, but it can confirm the diagnosis and help tailor follow-up, specialist care, and family planning.
Diagnosis
Teebi-Shaltout syndrome is usually diagnosed by looking at a pattern of features that are present from birth or become clearer in infancy or childhood, then confirming the findings with targeted testing. Getting a diagnosis is often a turning point toward answers and support. Because this condition is rare, the genetic diagnosis of Teebi-Shaltout syndrome often involves a genetics specialist who reviews appearance, growth, development, and family history together.
A doctor looks for physical features that fit Teebi-Shaltout syndrome and checks how growth and development are progressing. This visit often helps decide which genetic tests are most useful next.
A detailed family and health history can help show whether similar features, developmental concerns, or pregnancy findings have occurred in relatives. Family history is often a key part of the diagnostic conversation for rare genetic conditions.
Genetic tests are usually the main way to confirm the diagnosis of Teebi-Shaltout syndrome. These tests look for a disease-causing change in a gene linked to the condition or in a broader panel when the diagnosis is not yet certain.
Many living with Teebi-Shaltout syndrome are also assessed by specialists such as genetics, child development, or other pediatric teams depending on their symptoms. These evaluations help build a fuller picture and check for related health needs.
How is Teebi-shaltout syndrome diagnosed?
Teebi-Shaltout syndrome is usually diagnosed by a doctor who specializes in rare inherited conditions, based on the overall pattern of features a person has, their medical history, and sometimes their family history. Because this condition is very rare, there is not usually one simple test that makes the diagnosis on its own, so doctors may also use other exams or tests to rule out similar conditions, and genetic testing may help support the diagnosis if a related gene change is found.
Stages of Teebi-shaltout syndrome
Teebi-shaltout syndrome does not have defined progression stages. This rare genetic condition is usually present from early life and is identified by a pattern of physical features and developmental findings, rather than by a step-by-step worsening over time. Doctors usually start with a conversation about growth, development, and family history, along with a physical exam to look at features such as the face, hands, feet, and overall development. If Teebi-shaltout syndrome is suspected, genetic testing may help confirm the diagnosis, and follow-up focuses on monitoring the child’s needs rather than tracking early symptoms of Teebi-shaltout syndrome through set stages.
Outlook and prognosis
The outlook for people with Teebi-Shaltout syndrome is not well defined because it is extremely rare, but the condition is generally thought to be lifelong and non-progressive rather than degenerative. Prognosis depends on the severity of each person’s features, especially any developmental delay, feeding difficulties, growth concerns, or associated birth defects that may need ongoing care. Many affected individuals are expected to benefit from supportive management such as developmental therapies, educational support, and monitoring by specialists, which can improve day-to-day functioning and quality of life. Published information on mortality is very limited, and there is no clear evidence that the syndrome itself consistently shortens life expectancy. When major internal organ problems are absent, overall survival may be close to normal, although long-term outcomes can vary considerably from person to person.
Long-term effects
For many living with Teebi-Shaltout syndrome, the long-term picture is often shaped by how strongly the condition affects facial growth, development, and day-to-day function. Long-term effects vary widely, and some people have mainly physical differences in appearance while others also have developmental or sensory challenges. Because Teebi-Shaltout syndrome is very rare, the long-term effects of Teebi-Shaltout syndrome are not described in as much detail as they are for more common genetic conditions.
Facial and skull features present from birth often remain into adolescence and adulthood, although their appearance may change as the face grows. For many, this can mean ongoing differences in eye spacing, nose shape, forehead shape, or jaw alignment rather than a steadily worsening disease process.
If the eyes or eyelids are affected, some people may have long-term vision issues such as reduced sharpness of sight, eye strain, or trouble with eye alignment. In everyday life, this can show up as difficulty tracking words on a page or needing closer follow-up for sight problems.
Some people with Teebi-Shaltout syndrome may have lasting hearing differences or speech problems, especially if ear structure or palate development is affected. These effects can influence language development in childhood and clear communication later on.
In some children, early feeding difficulties or slower growth can have effects that carry into later childhood. Over time, daily routines may include ongoing differences in weight gain, eating efficiency, or oral development, depending on how strongly the syndrome affects the face and mouth.
How is it to live with Teebi-shaltout syndrome?
Living with Teebi-Shaltout syndrome can look very different from one person to the next, because this is a very rare genetic condition and its features can vary in type and severity. For many living with Teebi-Shaltout syndrome, daily life may include regular medical follow-up, help from therapists or school supports if developmental needs are present, and navigating social reactions to visible physical differences, which can affect confidence as much as health.
For parents, siblings, and other close caregivers, the condition often means extra appointments, advocacy, and emotional adjustment, especially when answers are hard to find because the syndrome is so uncommon. Even so, with coordinated care, practical support, and a strong circle of understanding people, many families build routines that help life feel more manageable and less defined by the diagnosis.
Treatment and drugs
Teebi-shaltout syndrome is usually treated by managing the specific health problems it causes, because there is no medicine that cures the underlying genetic condition itself. Treatment often looks different for each person, but it may include regular follow-up with specialists and supportive care for concerns such as growth, development, feeding, hearing, vision, or heart-related findings if these are present. Some children may benefit from physical, occupational, or speech therapy, while others may need surgery or other procedures to address structural differences or complications. Because Teebi-shaltout syndrome can affect people in different ways, care is usually tailored over time as needs become clearer.
Can you cure Teebi-shaltout syndrome?
No, there is no cure for Teebi-Shaltout syndrome at this time. Because it is a genetic condition people are born with, care focuses on managing the problems it can cause, with regular checkups, supportive therapies, and treatment for specific health needs if they come up. While this cannot remove the condition itself, it can help many living with Teebi-Shaltout syndrome stay as healthy and comfortable as possible.
Non-drug treatment
Day-to-day care for many living with Teebi-Shaltout syndrome often centers on communication, learning, movement, feeding, and regular developmental support rather than on medicines alone. Supportive therapies can help children build skills step by step and make daily routines easier at home, school, and clinic visits. Because Teebi-Shaltout syndrome can affect each child differently, treatment is usually tailored to the features and early symptoms of Teebi-Shaltout syndrome that are most noticeable. Care often works best when several specialists and therapists coordinate over time.
Developmental programs started in infancy or early childhood can support motor, language, and social skills as they emerge. For many, treatment begins not at the pharmacy, but with regular therapy sessions and guided practice at home.
Speech and language therapy can help with delayed talking, understanding words, and everyday communication. If speech is very limited, therapists may also introduce signs, picture systems, or communication devices.
Physical therapy can improve balance, coordination, posture, and overall strength when movement is delayed or awkward. It may also help with safe mobility, endurance, and confidence in play and daily activities.
Occupational therapy focuses on hand skills, dressing, feeding, play, and other daily tasks. Some strategies can slip naturally into your routine—like practicing grasping during meals or using easier-to-hold tools.
Your genes may have an impact on how drugs work for you
For people living with Teebi-Shaltout syndrome, there is no well-known, proven pattern showing that the syndrome itself changes how common medicines work. Care is usually based on the problems a person has, and medicine choices are guided by the same things doctors consider for anyone else, such as age, weight, other health issues, and how the body has responded to medicines before. In some situations, especially with medicines for seizures, pain, or surgery, inherited differences can affect how fast the body breaks down a drug, so doctors may sometimes need to adjust the type or dose based on the person rather than the syndrome.
Pharmacological treatments
There is no standard drug that treats the underlying cause of Teebi-Shaltout syndrome. Instead, treatment is usually based on the symptoms a person has, such as seizures, reflux, constipation, sleep problems, or behavior concerns. Medication is often just one chapter of care, alongside feeding support, therapies, and sometimes surgery.
Teebi-Shaltout syndrome does not have a proven disease-specific medicine at this time. When people look for medications for Teebi-Shaltout syndrome, the answer is usually symptom-based treatment rather than one single drug.
If seizures are part of Teebi-Shaltout syndrome, doctors may use anti-seizure drugs such as levetiracetam, valproate, or lamotrigine. The choice depends on seizure type, age, and side-effect profile.
If feeding is difficult because of acid reflux, medicines such as omeprazole or lansoprazole may be used to reduce stomach acid. Some children may instead be given famotidine, depending on symptoms and age.
For ongoing constipation, common options include polyethylene glycol and lactulose to soften stools and make bowel movements easier. Dosing may be increased or lowered gradually to improve comfort without causing diarrhea.
Genetic influences
If a child has Teebi-Shaltout syndrome, families often want to know whether future children could be affected too. Teebi-Shaltout syndrome is caused by changes in the SPECC1L gene, which helps tissues in the face and other parts of the body join and develop properly before birth. A change in a gene, sometimes called a variant, can affect health, and in this syndrome it leads to the pattern of physical features seen from birth. It usually follows an autosomal dominant inheritance pattern, which means one altered copy of the gene is enough to cause the condition, although some children are the first in the family to have it because the change happened new in them. Because signs can vary even among relatives with the same gene change, genetic testing for Teebi-Shaltout syndrome can help confirm the diagnosis and give clearer information about the chance of it happening again in a family.
Is Teebi-shaltout syndrome genetic?
Genetics are central to Teebi-Shaltout syndrome, which is linked to a disease-causing gene change. Genetic testing can help confirm Teebi-Shaltout syndrome and guide family counseling about recurrence risk in future pregnancies.
Having a genetic risk is not necessarily a diagnosis
Changes in genes are a normal part of human biology and are widely seen in the general population. Most of these changes do not have a direct effect on health and simply reflect natural human diversity. For many genes, having a variant associated with a condition suggests a possible link rather than a definite diagnosis, especially when more than one gene and environmental factors are involved. In some situations, though, a single well-studied variant in a particular gene can be enough to confirm the diagnosis.
Pharmacogenetics—how genetics influence drug effects
For people living with Teebi-Shaltout syndrome, treatment is usually based on the specific problems affecting daily life, not on one drug that treats the syndrome itself. Because Teebi-Shaltout syndrome is genetic, testing often helps most by confirming the diagnosis and helping the care team plan follow-up and supportive care. At this time, there are no widely established drug-gene rules showing that the genetic change behind Teebi-Shaltout syndrome reliably points to one best medicine or dose. Genetics is only one factor, and age, other medical conditions, and the symptom being treated can matter just as much when medicines are chosen. So if someone needs medication for related symptoms or health issues, doctors usually follow standard prescribing guidance, then adjust based on how well the medicine works and whether side effects appear. For many, this means that how genetics affect treatment for Teebi-Shaltout syndrome is more about guiding the overall care plan than predicting a specific response to a specific drug.
Interactions with other conditions
People living with Teebi-Shaltout syndrome usually need care that looks at the whole body, because its features can affect more than one organ system at the same time. Another important aspect is how it may link with other diseases: there are no well-established, disease-specific interactions known for Teebi-Shaltout syndrome in the way doctors see with some more common conditions, but related medical issues can still shape day-to-day health. For example, if someone has heart, breathing, feeding, or developmental problems alongside Teebi-Shaltout syndrome, those issues may add to fatigue, slow recovery from illness, or make treatments more complex. Interactions can look very different from person to person, especially because this syndrome is rare and the pattern of symptoms can vary. In practice, the main concern is careful coordination between specialists so that any additional condition, medicines, or surgery plans are reviewed together rather than treated separately.
How genes can cause diseases
Humans have more than 20,000 genes, each carrying out one or a few specific functions in the body. One gene instructs the body to digest lactose from milk, another tells the body how to build strong bones and another prevents the body's cells from beginning to multiply uncontrollably and developing into cancer. As all of these genes combined are the building instructions for our body, a defect in one of these genes can have severe health consequences.
Through decades of genetic research, we know the genetic code of any healthy/functional human gene. We have also identified that in certain positions on a gene, some individuals may have a different genetic letter from the one you have. We call these hotspots "Genetic Variations" or "Variants" in short. In many cases, studies have been able to show that having the genetic letter "G" in the position makes you healthy, but having the letter "A" in the same position disrupts the gene function and causes a disease. Genopedia allows you to view these variants in genes and summarizes all that we know from scientific research, which genetic letters (Genotype) have good or bad consequences on your health or on your traits.
What other conditions can cause similar symptoms to Teebi-shaltout syndrome?
Because Teebi-Shaltout syndrome is very rare and is often recognized by a pattern of face and head differences, it can sometimes be mistaken for other genetic conditions with similar features, especially Opitz G/BBB syndrome, Aarskog-Scott syndrome, and frontonasal dysplasia, which can also cause wide-set eyes and changes in the nose, forehead, or palate. If there are growth, heart, or learning concerns, doctors may also think about conditions such as Noonan syndrome or Kabuki syndrome, since the signs can overlap in some people.
History
Teebi-Shaltout syndrome entered the medical literature only fairly recently, so its history is much shorter than that of more familiar genetic conditions. Instead of being recognized over centuries, it was identified when specialists noticed that a small number of children shared a similar pattern of physical features and developmental findings. Those early descriptions gave doctors a starting point for recognizing Teebi-Shaltout syndrome as a distinct condition rather than a chance collection of unrelated symptoms.
First described in the medical literature as a rare syndrome seen in a limited number of families, Teebi-Shaltout syndrome was named after the physicians who helped characterize it. Because it is so uncommon, much of what is known has come from careful reports of individual children rather than from large studies. Early reports of Teebi-Shaltout syndrome focused on the features that were easiest to see in clinic, such as appearance, growth, and development, and later publications helped clarify which findings seemed to occur together most consistently.
As medical science evolved, doctors became better at separating very rare syndromes that can look alike at first glance. This mattered for Teebi-Shaltout syndrome, because many uncommon conditions share overlapping facial features or developmental concerns, especially in infancy and childhood. Over time, follow-up of reported families and improved testing made diagnosis more precise, and researchers were able to place the syndrome more clearly within the broader group of genetic developmental disorders.
Today, the history of Teebi-Shaltout syndrome is still being written. Many living with rare conditions are identified only when a clinician recognizes a pattern and connects it with earlier case reports, so every well-documented diagnosis can add to medical understanding. For families, that can mean that information remains limited, but it also means knowledge often grows steadily as more people are recognized and described in the medical literature.