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VERIFIED CONTENTAuthor: Katarzyna Wieczorek-Szukała, MD, PhD, medical biotechnologist, Medical University of Lodz

Rare diseases, despite the enormous advances in medicine, are still not fully researched. Some of them, due to the sporadic nature of the reported cases, remain the subject of incomplete, fragmented research, which in turn limits the spectrum of known and available therapies. Patients suffering from a rare disease very often struggle with the lack of appropriate support, diagnostics and disinformation. What diseases are rare diseases? How is their treatment going?

The basic problem with the qualification ofrare diseasesis that different countries have different definitions of the scope of this type of disease. In the European Union (including Poland) the disease will be considered rare if it affects up to 5 out of 10,000 people. In turn, in the United States, rare diseases are those affecting less than 200,000 people in the entire population.

So far, more than 7,000 rare diseases are known and new disease entities are diagnosed every year. It is estimated that around the world it affects 6 to 8% of the population. In general, even over 300 million people in the world live with such a wide group of sporadic diseases - so it is a much wider problem than it may seem at first glance.

What is a rare disease?

Rare diseasescan have many causes. The vast majority (over 70%) are diseases of genetic origin, resulting from a specific family history, birth defects or chromosomal changes.

Most often their course is chronic and progressive, and also leads to physical and mental disability. Almost 75% of them start already in childhood. In the vast majority of cases, rare diseases are misdiagnosed in the early stages, which delays appropriate countermeasures and allows the disease to progress.

Which are the most common rare diseases?

Rare diseases are a very heterogeneous group of diseases - among them there are narrower subgroups, including:

  • rare diseases of the blood and bone marrow (hemophilia, multiple myeloma),
  • storage diseases (cystic fibrosis, diseaseNiemann-Pick, Fabry's disease),
  • congenital defect syndromes (e.g. Prader-Willi syndrome),
  • neurological diseases (multiple sclerosis (MS), neuromuscular dystrophy, Huntington's chorea).

Some rare diseases, despite classifying them to this group, occur much more often than others, which translates into their easier recognition, and often also more effective therapies.

Examples of rare diseases

Multiple Sclerosis

Multiple Sclerosis (MS) is an autoimmune disease of the brain and spinal cord that affects the central nervous system. The incidence rate for this disease is on average 90 per 100,000 people, and in Poland, about 50,000 patients suffer from it.

The first symptoms of the disease appear at a relatively young age, between the ages of 20 and 40, and may include:

  • imbalance,
  • dizziness,
  • numbness and tingling in legs and arms,
  • painful muscle stiffness,
  • visual impairment,
  • chronic weakness,
  • emotional disorders.

As the disease progresses, symptoms worsen and patients suffer chronic limb tremors, impaired mobility, and even paralysis of one side of the body. The disease is incurable, and in the long term it causes permanent damage to nerves and glial cells, which entails both physical and mental changes.

The exact cause of multiple sclerosis is unknown, although a combination of genetic and environmental factors (including environmental pollution and vitamin D deficiency) are considered risk factors. Available therapies help patients to cope with attacks and bothersome symptoms of the disease.


Narcolepsy is a neurological condition involving a serious disturbance of natural sleep and the occurrence of uncontrolled sleepiness during the day. These symptoms are also accompanied by:

  • muscle loss attacks (also while awake),
  • hallucinations and hallucinations,
  • memory impairment,
  • nightmares.

It affects both men and women, can occur at any age and last throughout life. Statistics show that narcolepsy affects an average of 50 out of 100,000 people; however, this information does not necessarily reflect the real number. Affected individuals struggle with symptoms for years before a diagnosis is made.

Narcolepsy makes it difficult to function normally because patients can fall asleep while exercising everydayactivities, they also have difficulty distinguishing between dream experiences and reality. The exact cause of narcolepsy is unknown.

Probably the most important role in its development is played by some genetic mutations and an abnormal reaction of the immune system that can damage neurons in the brain.

Treatment of narcolepsy belongs to typical symptomatic therapies, where antidepressants and drugs supporting proper sleep phases. Helpful in relieving symptoms can be radical changes in lifestyle - avoiding stimulants in the form of caffeine, alcohol and reducing stressors.

Primary cholangitis

Formerly, this condition was known as primary cirrhosis of the liver. The rate of primary cholangitis is on average 40 per 100,000 people. It is much more often diagnosed in women (over 90% of cases), mainly in the age between 40 and 60 years. The clinical symptoms are so little specific that the disease develops over the years, and is often detected by accident on blood tests. The symptoms of primary cholangitis include :

  • chronic fatigue and weakness,
  • itchy skin,
  • occurrence of yellow skin lumps around the eyes (so-called jaundice).

Pains appear relatively rarely in the area of ​​the right side (hypochondrium). The genesis of the disease is most likely autoimmune changes involving the gradual destruction of cells of the small bile ducts. Their degradation impairs the secretion and transport of bile, which is necessary for the emulsification of fats, regulating the level of cholesterol and filtering metabolic products.

The obstructed outflow of bile from the liver and its stagnation (the so-called cholestasis) leads to its scarring and even cirrhosis. Medicine does not offer a drug to combat the causes of primary cirrhosis.

It is important, however, to identify the symptoms as early as possible, thanks to which it will be possible to more effectively slow the progression of the disease (e.g. by pharmacologically supporting the outflow of bile).

Fabry disease

This rare condition affects approximately 30 out of 100,000 people and belongs to the group of storage diseases. It is caused by genetic changes - specifically a mutation in the gene encoding the protein of the α-galactosidase enzyme.

The deficiency of this enzyme in the body causes the deposition of ceramide derivatives in the tissues and walls of blood vessels, which impairs the functioning of many organs.

This disease can be inherited in a gender-linked manner, and it manifests itself more strongly in men. The most overwhelming symptoms of this ailmentdiseases are the so-called Fabry breakthroughs - that is, long-lasting attacks of very strong, burning and excruciating pain - appearing initially around the joints of the arms and legs, then throughout the body. Additionally, there are also:

  • burning or tingling sensation in the hands or feet,
  • imbalance,
  • heart rhythm disturbance,
  • sweat secretion disorder,
  • sensitivity to cold and heat,
  • kidney damage,
  • eye dysfunction.

There are two types of treatment for Fabry disease:

  • enzyme replacement therapy (by administering the enzyme alpha-galactosidase intravenously)
  • or taking a drug called migalastat. The therapy, however, is extremely expensive and requires multiple repetitions.

Cystic fibrosis

Cystic fibrosis (CF), also known as cystic fibrosis, is a genetic disease in which the secretion of exocrine glands is disturbed. The patient's organism produces too sticky mucus, disrupting the functioning of all organs with mucous glands.

The most common changes therefore occur within two systems - respiratory (causing recurrent infections and respiratory failure) and digestive (damaging the pancreas and leading to its failure).

Cystic fibrosis affects about 25 out of 100,000 people and is more common in Europeans.

The accompanying symptoms, often occurring from early childhood, include :

  • chronic and persistent cough,
  • recurrent bronchitis and pneumonia,
  • spitting blood,
  • sinusitis,
  • too large, fatty stools in newborns,
  • stomach pains,
  • intestinal obstruction.

In adults, cystic fibrosis also affects infertility and the subsequent development of secondary diabetes. Treatment of cystic fibrosis is mainly based on fighting its symptoms. In the pulmonary form, the therapy is based on removing thick secretions from the respiratory tract and supporting existing infections and inflammations with antibiotics.

Symptoms of the digestive tract are relieved, among others Enzyme supplements to aid digestion and absorption of nutrients, and a strict diet.

Problems with treating rare diseases

As can be seen in the above examples, rare diseases are a very heterogeneous group of diseases with different genesis, course and prognosis. Although together they cover a significant number of people (up to 3 million citizens in Poland), specific cases of rare or ultra-rare diseasesseveral or a dozen people suffer. Their treatment requires an interdisciplinary approach and access to the latest medical technologies, often unavailable to patients for financial reasons.

Over the years, rare diseases have never been included in the lists of reimbursed or priority programs - both in Poland and other European countries. Fortunately, this approach is gradually changing and the need for intensive support for this particular group of patients is increasingly recognized. In 2022, the Plan for Rare Diseases (planned for 2022-2023) was adopted in our country, containing specific actions to realistically improve the situation of patients with rare diseases.

Additionally, the Medical Research Agency announced the first research and development program in Central and Eastern Europe, intended in particular for patients suffering from a rare disease. As much as PLN 100 million was allocated to specialist diagnostics, development of clinical trials and modern drug therapies.

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