What’s the Difference Between a Syndrome and a Disease?

The words "syndrome" and "disease" are often used interchangeably, but they have some important differences.

The classification, though, has no bearing on whether they're real illnesses or how serious they are. It's simply a matter of how well they're understood.

This article examines the differences between a syndrome and a disease and provides examples of both.

What Is a Syndrome?

The definition of a syndrome is pretty straightforward:

• A collection of signs and symptoms known to frequently appear together that suggest the presence of a disease or an increased chance of developing one

In typical medical usage, a syndrome often doesn't have an understood cause, course, or underlying process. This generally means treatments are lacking and there's no known cure.

When doctors designate something a syndrome, they're essentially saying, "We recognize this cluster of symptoms but we don't yet know what's going on."

That doesn't mean the symptoms aren't real or aren't serious, it just means medical science hasn't yet determined why they're happening.

Common Syndromes

Examples of syndromes and their primary symptoms are:

• Metabolic syndrome: Abnormalities in blood sugar, blood pressure, body fat, cholesterol, and triglycerides that are tied to the development of heart disease and type 2 diabetes
• Fibromyalgia: Chronic widespread pain, extreme fatigue, cognitive dysfunction
• Restless legs syndrome: Unusual sensations when the legs are at rest that are temporarily relieved by movement
  
• Irritable bowel syndrome: Chronic digestive symptoms often tied to specific foods
• Myofascial pain syndrome: Painful trigger points in muscles and connective tissues, often as a result of injuries
• Vulvodynia: Chronic pain in the vulva (outer portion of the female genitalia) with no known cause
• Interstitial cystitis: Also called painful bladder syndrome
• Multiple chemical sensitivity: Abnormal reactions to small amounts of chemicals, especially those with strong odors
  

Many conditions start out as syndromes and are then re-classified as a disease once more is known about them. If the name of the illness contains the word syndrome, it may or may not be changed.

What Is a Disease?

The definition of disease is a little more complicated than that of syndrome. You can find several, incuding:

• A disordered or incorrectly functioning organ, part, structure, or system of the body resulting from the effect of genetic or developmental errors, infection, poisons, nutritional deficiency or imbalance, toxicity, or unfavorable environmental factors
• A definite pathological process having a characteristic set of signs and symptoms. It may affect the whole body or any of its parts and its etiology, pathology, and prognosis may be known or unknown

The second definition especially doesn't seem to do a good job of separating a disease from a syndrome. In common medical usage, though, a disease is generally considered to have:

• A known cause
• Clear symptoms
• Accepted treatments

Common Diseases

Examples of disease and their causes are:

• Chickenpox: Varicella-zoster virus
• Influenza (flu): Influenza viruses
• Common cold: Rhinoviruses and many other viruses
• Mononucleosis: Epstein-Barr and other viruses
• COVID-19: SARS-CoV-2 virus (in the coronavirus family)
• Parkinson's disease: Loss of nerve cells in an area of the brain
• Rheumatoid arthritis and other autoimmune diseases: The immune system attacking healthy parts of the body
• Cancer: Changes in DNA (genetic material) that cause cells to divide abnormally and spread into surrounding tissues
  

Summary

A syndrome is a group of signs and symptoms that are known to go together but don't have a clear cause, course, or treatment path.

A disease is a disorder that affects how your body functions and is more likely to have a known cause, a distinct course, and established treatments.

If you're diagnosed with a syndrome, you may run into people who don't think it's serious or "real" because it's not a disease. This isn't the case. It really just means that medical science hasn't figured it out yet.