Dictionary > Syndrome


n., plural: syndromes
Definition: The collection of symptoms as a result of an abnormality or disease

Definition Of Syndrome

A syndrome is a collection of signs, symptoms, series of events, and/or characteristics that occur together and indicate a particular medical condition, disorder, or disease. In biology and medicine, it is a term that refers to a group of related clinical features that individuals with such a condition typically experience. Syndromes can be a tool for healthcare professionals in diagnosing specific conditions. They provide a framework by which a complex health issue may be understood, recognized, and thereby, aptly addressed.

When do we use the term syndrome? What is its difference from a disorder or a disease? Let’s find out below!

Watch this vid about the term “syndrome”:

Biology definition:
A syndrome is a collection of signs, symptoms, a series of events, and/or characteristics that occur together and indicate a particular medical condition or disease. An example is Down Syndrome caused by a particular abnormality in the chromosome complement of the human genome.

  • Etymology

The word “syndrome” came from the Greek words “syn”, meaning “together” and “dromos”, meaning “a running” or “a course“. Thus, when translated, it means a running together or a concurrence. Its use dates back to the 16th century to pertain to a group of symptoms or signs indicative of specific diseases. Now, its usage broadened, encompassing recognizable patterns of signs and symptoms that occur together or concurrently, indicating a particular medical condition

  • Syndrome vs. Disease vs. Disorder

Can you use the terms “syndrome”, “disease” and “disorder” interchangeably? While some do use them interchangeably as these terms may all pertain to a condition beyond what is generally considered medically, biologically, or physiologically “normal” or “regular”, these terms have specific usages in medicine and biology.

Let us first take the word “disease”. It refers to a condition with an established biological cause, producing a defined group of symptoms. It is generally distinct and measurable. Conversely, a syndrome is a collection of signs and symptoms associated with a disease. Knowing the syndrome may help health professionals diagnose a disease.

The exact cause of a syndrome may hardly be traced. In fact, the cause may not involve just a single cause but a set of related causes.

When a condition has initially been named a syndrome, and then, in time, the underlying cause has been identified, the name is retained rather than relabeled as a disease or a disorder. An example is Down Syndrome with characteristic features such as a flattened face, a short neck, small ears, upward-slanting eyelids, a protruding tongue, tiny white spots on the iris, small hands and feet, palmar crease, poor muscle tone or loose joints, developmental delays, and intellectual disability. Later, the underlying cause has been attributed to an extra chromosome 21. (CDC, 2023)

A disorder, in turn, is an interruption to what’s typical, normal, or regular. It is a deviation from the normal functioning. For example, arrhythmia is a condition characterized by an irregular heartbeat. Such a condition is not a disease but a disorder resulting from disease, e.g., cardiovascular disease. And while a disease has a specific or definite cause, the cause of a disorder may not be apparent (similar to some syndromes).

While the terms “syndrome” and “disorder” at times overlap, the term “disorder” has a wider range of disruptive conditions, affecting various aspects of an organism, such as structure, behavior, and function.

Common Characteristics Of Syndromes

Syndromes have common characteristics such as the following:

  1. Association of Symptoms. Syndromes have a set of signs and symptoms that occur together, especially as they are associated with particular diseases. This makes them different from other conditions with unrelated or isolated symptoms. In syndromes, multiple symptoms may affect different organ systems or aspects, which occur collectively defining the condition.
  2. Consistency. In syndromes, there is a pattern of signs and symptoms that occur consistently across affected individuals. While there may be some degree of variation in the severity or presentation of symptoms, the core characteristics of the syndrome remain relatively stable.
  3. Underlying Cause. Syndromes, as already pointed out earlier, may have known causes or they may have unknown etiologies. The cause may be a genetic mutation, a chromosomal abnormality, an environmental factor, or a set of or a combination of these factors.

Causes And Classification Of Syndromes

What are the causes of syndromes? How are syndromes classified? Let’s find out below.

  • Genetic Syndromes

Genetic syndromes are syndromes characterized by changes in the genetic material. These changes may be inherited or they may arise spontaneously. Genetic syndromes may be in the form of chromosomal abnormalities, single gene mutations, or multifactorial inheritance.

  1. Chromosomal abnormalities. Some syndromes are caused by abnormalities in the structure of the chromosome or by the number of chromosomes occurring in a cell. Examples: Down syndrome, where there is an extra copy of chromosome 21, and Turner syndrome, which occurs due to the complete or partial absence of one X chromosome.
  2. Single gene mutations. Some syndromes arise due to a mutation involving a specific gene. Examples of single-gene mutation syndromes are cystic fibrosis and Duchenne muscular dystrophy.
  3. Multifactorial inheritance. There are also syndromes that are caused not just by genetic factors but also by environmental factors that interact with certain genes and thereby have an impact on their expression. Examples are neural tube defects (abnormalities due to incomplete development or closure of the neural tube during embryonic development), which are influenced by both genetic (e.g., mutation in the MTHFR gene) and environmental factors (e.g., the availability of folate during early pregnancy, exposure to certain chemicals such as pesticides and certain medications, etc.).
  • Acquired Syndromes

Acquired syndromes develop due to factors that are acquired later in life. They are not directly linked to genetic factors. Examples are syndromes caused by environmental factors, infections, or exposures to certain toxins or chemicals.

  1. Environmental factors. Syndromes may arise after having been exposed to certain conditions or agents present in the environment. Example: fetal alcohol syndrome caused by maternal alcohol consumption during pregnancy
  2. Infections. Infection caused by viruses, bacteria, and other pathogens may lead to syndromes. Examples: congenital rubella syndrome and acquired immunodeficiency syndrome (AIDS)
  3. Toxic exposures. Exposure to toxins, chemicals, or medications may lead to the development of certain syndromes. Example: fetal exposure to certain medications like thalidomide can result in a specific set of birth defects known as thalidomide embryopathy

Clinical Presentation Of Syndromes

The clinical presentation of medical syndromes may vary depending on age, gender, and overall health. Nevertheless, a particular syndrome would have a pattern of signs and symptoms distinctive to a medical condition. Often, syndromes manifest as follows:

  • Physical features. Affected individuals tend to show common characteristic features, such as dysmorphic figures involving the face, head, hands, or other body parts and growth abnormalities (e.g., disproportionate height and weight)
  • Developmental and cognitive impairments. Syndromes may manifest in the learning capacity and intellectual ability of the affected individuals. Depending on the severity of the syndrome, it may present as a delayed developmental milestone (e.g., delays in learning to walk, sit, or speak) or as an intellectual disability, i.e., affecting the individual’s capacity to learn and solve problems.
  • Biological issues. Some syndromes may manifest at the cell level, organ level, or system level. Examples are syndromes presenting as liver dysfunction, heart defect, kidney abnormality, hearing loss, visual impairment, problems with proprioception (awareness of body position), hormonal imbalance, or immune system dysregulation.


What are “signs” and “symptoms” in the context of medicine?

The terms “signs” and “symptoms” are two aspects that can easily overlap. However, there are subtle differences.

  • Signs are features of a medical condition that can be observed or measured by healthcare professionals.
  • Symptoms are features of a medical condition that are reported by the patient or individual affected by it. They may not be directly observable by healthcare professionals.

In summary, while signs are objective, symptoms are rather subjective, depending on how the patient experiences them. Thus, symptoms may vary in intensity among individuals as the symptoms largely depend on how an individual perceives and interprets them.

Diagnosis And Evaluation Of Syndromes

Syndromes are assessed through clinical assessment (e.g., medical history, physical examination, and family history), laboratory and genetic testing (e.g., chromosomal analysis, genetic sequencing, and metabolic testing), and imaging studies (e.g., X-rays, ultrasound, MRI or CT scans).

Healthcare providers often combine the use of these assessments or diagnostic tools in order to arrive at an accurate diagnosis. This is essential as they can be used as the basis for a specific treatment tailored to individuals.

Let’s take a look at some of these tools below:

  • Clinical assessments are done by gathering information about the individual’s medical history and family history. Physical examination is also conducted to find out any dysmorphic features, growth abnormalities, and other physical signs associated with a particular syndrome.
  • Chromosomal analysis. This tool is essential in detecting chromosomal aberrations, such as chromosomal deletions, duplications, or translocations.
  • Genetic sequencing. DNA sequencing is one of the common techniques used in identifying genetic mutations, especially those associated with the syndrome under investigation.
  • Metabolic testing. This entails analyzing blood, urine, or tissue samples so as to identify errors in metabolic pathways.
  • Imaging studies are used to gather information on the structure of organs and tissues. X-rays, for instance, are used in assessing bones and skeletal abnormalities. Ultrasounds are used for assessing internal organs. MRI and CT scans, in turn, provide detailed cross-sectional images during the evaluation of organ structure and function.

Examples Of Common Syndromes

These are a few of the many examples of syndromes in humans.

  • Chronic fatigue syndrome

Chronic fatigue syndrome (CFS), also known as myalgic encephalomyelitis (ME), is characterized by persistent fatigue that cannot be improved with rest or sleep. The individual would thus experience cognitive difficulties (“brain fog”), headaches, problems with concentration and memory, muscle and joint pain, and sore throat. The exact cause is unclear and apparently a combination of factors, e.g., genetic and environmental factors, hormonal imbalances, and immune dysfunction.

  • Irritable bowel syndrome

Irritable bowel syndrome (IBS) is a gastrointestinal condition characterized by abdominal pain or discomfort that can be relieved by passing stool, changes in bowel habits (having the urge to pass stool frequently or difficulty passing stool), flatulence, bloating, and abdominal distention. The exact cause is also not well understood but may be associated with gut-brain axis abnormality resulting in altered intestinal motility, increased gut sensitivity, or changes in the gut microbiota.

  • Asperger’s syndrome

Asperger’s syndrome is a type of autism spectrum disorder (ASD). People with Asperger’s syndrome typically experience poor social skills. They are not socially driven. They are masters of routine, exhibiting restricted and repetitive patterns of behavior, interests, or activities. Despite these challenges, they often have average to above-average intelligence. They have artistic inclinations and extreme focus on specific topics of interest.

  • Turner syndrome

Turner syndrome is a genetic condition affecting females caused by the complete or partial absence of the second X chromosome. They often have short stature, webbed neck, low hairline, low set ears, narrow, high-arched palate, and broad chest with widely spaced nipples. They may experience fertility issues, hormonal imbalances, and heart defects.

Clinical signs of Turner syndrome
Clinical signs of Turner syndrome. Image Credit: Medizzy.com.
  • Fragile X syndrome

Fragile X syndrome is an inherited genetic condition affecting both males and females. Common facial features include an elongated face, a broad forehead, large protruding ears, and a prominent lower jaw. Other clinical signs include macroorchidism (enlarged testicles in males), increased joint mobility, and mental problems. The cause is a mutation in the FMR1 (Fragile X Mental Retardation 1) gene located on the X chromosome, resulting in a reduced or lack of the production of the protein fragile X mental retardation protein (FMRP), which is important for normal brain development and function.

Fragile X syndrome clinical signs in men
Fragile X syndrome clinical signs in men. Image Credit: inviTRA.


“Future Prospects In Understanding And Managing Syndromes”

The field of syndromes research is continuously advancing. Advances in genetic testing and diagnosis, precision medicine approaches, and the development of gene therapies offer promising avenues for the future:

  • Next-generation sequencing technologies, such as whole-exome sequencing and whole-genome sequencing, will help identify the genetic variations associated with syndromes.
  • Precision medicine, as the name implies, is a targeted intervention in which the treatment will be based on the specific genetic makeup, environmental factors, and unique characteristics of an individual.
  • Gene therapies (gene modulation, gene editing, and gene replacement) may soon give rise to breakthrough treatments at the genetic level for treating difficult medical conditions, including syndromes

By harnessing these advancements, we can expect improved diagnostic accuracy, targeted treatments, and enhanced supportive care for individuals with syndromes. Ongoing research efforts hold the potential to unravel the underlying mechanisms, identify new syndromes, and improve our understanding of the complexities associated with these conditions.

Take the Syndrome – Biology Quiz!


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1. What is a syndrome?

2. Etymology of 'syndrome'

3. A medical condition characterized by symptoms and with an established biological cause

4. Which of these is a characteristic of a syndrome?

5. What are acquired syndromes?

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  11. Ng, S. B., Buckingham, K. J., Lee, C., Bigham, A. W., Tabor, H. K., Dent, K. M., … & Aburatani, H. (2010). Exome sequencing identifies the cause of a Mendelian disorder. Nature Genetics, 42(1), 30-35.
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