Nosology () is the branch of medical science that deals with the classification of diseases. Fully classifying a medical condition requires knowing its cause (and that there is only one cause), the effects it has on the body, the symptoms that are produced, and other factors. For example,

influenza Influenza, commonly known as "the flu", is an infectious disease caused by influenza viruses. Symptoms range from mild to severe and often include fever, runny nose, sore throat, muscle pain, headache, coughing, and fatigue. These symptom ...

is classified as an infectious disease because it is caused by a virus, and it is classified as a respiratory infection because the virus infects and damages certain tissues in the respiratory tract. The more that is known about the disease, the more ways the disease can be classified nosologically. Nosography is a description whose primary purpose is enabling a diagnostic label to be put on the situation. As such, a nosographical entity need not have a single cause. For example, inability to speak due to advanced dementia and an inability to speak due to a stroke could be nosologically different but nosographically the same.

Types of classification

Diseases may be classified by cause, pathogenesis ( mechanism by which the disease progresses), or by

symptom Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign for example may be a higher or lower temperature than normal, raised or lowered blood pressure or an abnormality showi ...

(s). Alternatively, diseases may be classified according to the organ system involved, though this is often complicated since many diseases affect more than one organ. A chief difficulty in nosology is that diseases often cannot be defined and classified clearly, especially when cause or pathogenesis are unknown. Thus diagnostic terms often only reflect a symptom or set of symptoms ( syndrome). Traditionally diseases were defined as syndromes by their symptoms. When more information is available, they are also defined by the damage they produce. When cause is known, they are better defined by their cause, though still important are their characteristics. This leads to a branching differentiation in which a clinical syndrome (pattern of signs and symptoms) can come to be understood as a nonspecific finding shared by a group of disease entities or endotypes. For example, concepts such as murrain and the grippe that were formerly undifferentiable to humans and thus understood as a single disease later can be logically unraveled as separate diseases with similar

clinical presentation In a physical examination, medical examination, or clinical examination, a medical practitioner examines a patient for any possible medical signs or symptoms of a medical condition. It generally consists of a series of questions about the pat ...

s. Thus, nosology is dynamic, reclassifying as science advances. The advent of

molecular biology Molecular biology is the branch of biology that seeks to understand the molecular basis of biological activity in and between cells, including biomolecular synthesis, modification, mechanisms, and interactions. The study of chemical and phys ...

brought a further reclassification potential with the concept of molecularly defined diseases, defined by their molecular characteristics. This concept was introduced in 1949, with the seminal paper, "

Sickle Cell Anemia, a Molecular Disease "Sickle Cell Anemia, a Molecular Disease" is a 1949 scientific paper by Linus Pauling, Harvey A. Itano, Seymour J. Singer and Ibert C. Wells that established sickle-cell anemia as a genetic disease in which affected individuals have a different ...

", in ''Science'' magazine,

Linus Pauling Linus Carl Pauling (; February 28, 1901August 19, 1994) was an American chemist, biochemist, chemical engineer, peace activist, author, and educator. He published more than 1,200 papers and books, of which about 850 dealt with scientific topi ...

, Harvey Itano and their collaborators laid the groundwork for establishing the field of molecular medicine. Molecular medicine, in concert with genetics and genomics as aspects of molecular biology, provided new instances of the theme that clinical presentations that humans formerly interpreted as a single disease can be subclassified into a group of disease entities or endotypes. For example, many OMIM database entries show the pattern of disease name XYZ with types identified as XYZ1 (involving sequence variants in gene A), XYZ2 (involving sequence variants in gene B), XYZ3 (involving sequence variants in gene C), XYZ4 (involving sequence variants in both genes B and C), and so on.

Coding systems

Several classifications of diseases have been historically proposed, and normally all of them assign a code to every supported disease. Some of them codify diseases following the path of the classification tree, and others like SNOMED use a multifactor classification system. The most known coding system is the

World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level o ...

ICD-Series, but there are other accepted classifications like DOCLE,

NANDA Nanda may refer to: Indian history and religion * Nanda Empire, ruled by the Nanda dynasty, an Indian royal dynasty ruling Magadha in the 4th century BCE ** Mahapadma Nanda, first Emperor of the Nanda Empire ** Dhana Nanda (died c. 321 BCE), last ...

or SNOMED. Historically there were others like the Berkson Coding System that are not maintained anymore. There are also coding systems for symptoms present in the diseases and biological findings. They are normally included in medical dictionaries, also with a codification system. Some of them are MeSH (Medical Subject Headings), COSTART (Coding Symbols for Thesaurus of Adverse Reaction Terms) or MedDRA (Medical Dictionary for Regulatory Activities) Other systems like

Current Procedural Terminology The Current Procedural Terminology (CPT) code set is a procedural code set developed by the American Medical Association (AMA). It is maintained by the CPT Editorial Panel. The CPT code set describes medical, surgical, and diagnostic services and ...

do not deal directly with diseases but with the related procedures.

Extended nosology and general medical conditions

In a wide sense, nosology deals not only with diseases, but with any kind of medical condition, like injuries,

lesions A lesion is any damage or abnormal change in the tissue of an organism, usually caused by disease or trauma. ''Lesion'' is derived from the Latin "injury". Lesions may occur in plants as well as animals. Types There is no designated classifi ...

or disorders. Medical conditions, like diseases, can be defined by cause, pathogenesis ( mechanism by which the disease is caused), or by a collection of

s, medical signs and biomarkers, particularly when the other two definitions are not available ( idiopathic diseases). From a nosological point of view, medical conditions can be divided in disorders, diseases, syndromes, lesions and injuries, each one with some specific meaning, as listed at '' Disease § Terminology''.

History

Ancient medical treatises had a variety of different ways of classifying and grouping illnesses. Chinese texts like the '' Huangdi Neijing'' categorized diseases by which of the atmospheric influences was believed to be responsible for them. Many ancient Greek, Mesopotamian, Roman, and Egyptian authors categorized diseases by the body parts they affected, while others divided diseases into

acute Acute may refer to: Science and technology * Acute angle ** Acute triangle ** Acute, a leaf shape in the glossary of leaf morphology * Acute (medicine), a disease that it is of short duration and of recent onset. ** Acute toxicity, the adverse ef ...

or chronic illnesses. Mental disorders were classified into categories like

mania Mania, also known as manic syndrome, is a mental and behavioral disorder defined as a state of abnormally elevated arousal, affect, and energy level, or "a state of heightened overall activation with enhanced affective expression together wi ...

and

paranoia Paranoia is an instinct or thought process that is believed to be heavily influenced by anxiety or fear, often to the point of delusion and irrationality. Paranoid thinking typically includes persecutory beliefs, or beliefs of conspiracy c ...

Hippocrates Hippocrates of Kos (; grc-gre, Ἱπποκράτης ὁ Κῷος, Hippokrátēs ho Kôios; ), also known as Hippocrates II, was a Greek physician of the classical period who is considered one of the most outstanding figures in the history o ...

, and this system was utilized by later authors like

Najib ad-Din Samarqandi Najib ad-Din Abu Hamid Muhammad ibn Ali ibn Umar Samarqandi was a 13th-century Persian physician from Samarqand. Samarqandi died during the Mongol attack on Herat, in Afghanistan, in 1222CE. He was a prolific medical writer and expositor of medic ...

. Many popular ancient disease classification systems largely relied upon

humorism Humorism, the humoral theory, or humoralism, was a system of medicine detailing a supposed makeup and workings of the human body, adopted by Ancient Greek and Roman physicians and philosophers. Humorism began to fall out of favor in the 1850s ...

, which carried over into medieval times. Early attempts to develop more comprehensive approaches to the classification of diseases were made by Jean Fernel in the 16th century. Early modern nosological efforts grouped

disease A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that a ...

s by their

s, whereas modern systems focus on grouping diseases by the

anatomy Anatomy () is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old science, having i ...

and cause involved. In the 17th century, the English physician Thomas Sydenham was the first to propose a syndrome-based classification of diseases. For Sydenham a disease and a syndrome were equivalent concepts. In the 18th century, the taxonomist

Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement in 1761 as Carl von Linné Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, ...

, Francois Boissier de Sauvages, and psychiatrist Philippe Pinel developed an early classification of physical illnesses. In the late 19th century, Emil Kraepelin and then

Jacques Bertillon Jacques Bertillon (11 November 1851 – 4 July 1922) was a French statistician and demographer. Born in Paris, Bertillon was the son of statistician Louis Bertillon and the older brother of Alphonse Bertillon. He was educated as a physicia ...

developed their own nosologies. Bertillon's work, classifying causes of

death Death is the irreversible cessation of all biological functions that sustain an organism. For organisms with a brain, death can also be defined as the irreversible cessation of functioning of the whole brain, including brainstem, and brain ...

, was a precursor of the modern code system, the International Classification of Diseases.

Applications

* Nosology is used extensively in

public health Public health is "the science and art of preventing disease, prolonging life and promoting health through the organized efforts and informed choices of society, organizations, public and private, communities and individuals". Analyzing the det ...

, to allow

epidemiological Epidemiology is the study and analysis of the distribution (who, when, and where), patterns and determinants of health and disease conditions in a defined population. It is a cornerstone of public health, and shapes policy decisions and evid ...

studies of public health issues. Analysis of death certificates requires nosological coding of causes of death. * Nosological classifications are used in medical administration, such as filing of health insurance claims, and patient records.

References

External links

{{Commons category
International Classification of Diseases (ICD-10)
by the

Medical terminology