Rare or Infrequent Diseases, including those of genetic origin, are those diseases that have a low frequency (prevalence), less than 5 cases per 10,000 inhabitants in the community, or 1 born per 2000 inhabitants according to the definition of art. . 2 inc. a) of provincial law 6814.

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The concept of Rare Diseases, also known as "rare diseases", "orphan diseases", "rare diseases" or "rare diseases", are a group of diseases that have certain common characteristics:

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• They appear with a low frequency, which in the Province is determined as less than 1 case per 2,000 inhabitants

• They present many diagnostic and follow-up difficulties

• They have an unknown origin in most cases

• They involve multiple health, social, psychological, educational and work problems

• There are few epidemiological data

• They pose difficulties in the investigation due to the few cases

• They mostly lack effective treatments

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Most cases of rare or infrequent diseases appear in pediatric age, a direct consequence of the high frequency of diseases of genetic origin and the presence of congenital anomalies.

However, the prevalence is higher in adults than in children, due to the excessive mortality of some childhood diseases, such as malformations or serious genetic diseases, and also due to the influence of certain diseases whose age of onset is later, such as certain autoimmune diseases. , amyotrophic lateral sclerosis or genetic diseases such as Wilson's or Huntington's disease, among others.

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It is not easy to decide which are the groups of rare or infrequent diseases, as there are about 7000. They are usually grouped according to criteria such as what may be the cause, or what organ or part of the body may be affected.

Nor is its classification and codification easy. When a disease is not on a recognized list of diseases, it is as if it did not exist. On the other hand, there is more than one list that includes ER, that is, there is no consensus on a single inventory of this type of disease.