Processes of disease

2.2 Processes of disease

Chapter 2.2a Processes of disease

Learning points

Processes of disease

‘Pathogenesis’ (literally ‘the birth of disease’) is the term used to describe the pathology of how disease develops. The diverse forms of the disease process can be grouped into seven broad categories:

From the perspective of the study of clinical medicine, classification of the processes of disease is important because it generates principles of causation of disease that can then be applied to all diseases. For example, if the process of inflammation is understood, then this will aid in the study of any one of the diseases that involves inflammation, such as arthritis, dermatitis, meningitis and pneumonia. Because the understanding of these basic processes of disease is fundamental to the study of the pathology of all diseases, they are explored in some depth in this text. The topics of inflammation, abnormal immune mechanisms, thrombosis, embolism and infarction, and tumours (cancer) are the subjects of the next four chapters.

Degeneration is the result of ageing. In general, ageing involves cell loss and atrophy of tissues. Rapidly regenerating active tissue may become replaced with tough, fibrous, less-active tissue, and organs may cease to function as effectively. Deformities (e.g. of skin, joints or bones) become commonplace. Degenerative diseases will be discussed in later chapters according to the physiological system which they affect.

The category of metabolic abnormality embraces all diseases that develop when the homeostatic function for metabolism (the chemical processes that go on continuously in living cells) becomes imbalanced. Again, the metabolic disorders are discussed throughout the text according to the physiological system which they affect.

The principles of genetic (congenital) abnormalities are presented in Chapter 1.1b, under the heading ‘Mutation’.

An understanding of the processes of disease can also aid thinking about disease from the perspective of another medical system. If it is possible to consider each process of disease in terms of corresponding pathological descriptions described in another medical system, then it is possible to take these correspondences and use them to help describe pathological processes in all manner of diseases. For example, inflammation always involves the generation of redness and heat in tissues. According to Chinese medicine, redness and local heat always corresponds to the Pathogenic Factor of Heat. Therefore, it would be reasonable to conclude that all inflammatory diseases will be described, amongst other things, in terms of Heat in Chinese medicine. In this chapter, all the processes of disease are also interpreted in terms of Chinese medicine, and this will provide the foundation for the Chinese medicine interpretations of all the individual diseases described later in the text (see Q2.2a-2)image.

In summary, it cannot be overstated how much the understanding of the basic processes of disease can enrich the understanding of conventional pathology and how it might relate to another medical system such as Chinese medicine.

image Information Box 2.2a-I Processes of disease: comments from a Chinese medicine perspective

As a general introduction, it is important to explain the rationale for comparing the conventional view of the processes of diseases with a Chinese medicine understanding of pathology. As stated in the text, in the study of clinical medicine classification of the processes of disease is important because it generates principles of causation of disease, which can then be applied to all diseases. For example, an understanding of the process of inflammation will aid in the study of any disease that involves inflammation, such as arthritis, dermatitis, meningitis and pneumonia.

The important aspect of this system of classification is that, although the understanding of conventional processes would have involved knowledge that would not have been known to the ancient Chinese, the manifestations of the processes in signs and symptoms are consistent within each process. It is these that are the bridge between the two systems of medicine.

Inflammation will always have characteristics of heat and swelling, and degeneration will always involve a drying and withering of tissue. As observable phenomena, these would form the basis for making a diagnosis in Chinese medicine. However, the way in which the heat and swelling is generated in each individual case does not share the same consistent internal process as understood in the conventional view, and looking for parallels of process is a trap for the unwary.

When a patient presents with a condition that results from one or more of the seven processes of disease, it can reasonably be expected that the symptoms and signs normally associated with those processes are evident. The meaning and importance of the signs and symptoms can then be assessed within the entirely different understanding of the manifestation of symptoms and signs described in Chinese medicine. What this means is that the symptoms and signs of the conventionally described processes of disease will help point to the Chinese medicine syndromes that might be expected to be discerned in any medical condition, first assuming the underlying process of disease is recognised.

image Self-test 2.2a Processes of disease


1. Inflammation: a response of tissues to damage.

Tumours: excessive cell production leading to the development of a mass.

Abnormal immune mechanisms: due to the normally protective immune system producing undesirable effects.

Thrombosis, embolism and infarction: due to increased clotting of blood or abnormal changes in the blood vessel walls.

Degeneration: due to deterioration of the body structures.

Metabolic abnormalities: a loss of balance of the usual chemical processes that comprise metabolism.

Genetic abnormalities: disease that is present in the fetus before birth, either due to a mutation of one of the gametes or to a mutation occurring during the development of the fetus.

2. Examples of diseases are too various to list. Refer to the table in the answer to the last question to check your answers.

3. Simple energetic interpretations of the seven process of disease are:

Chapter 2.2b Inflammation

Learning points

Physiology of acute inflammation

‘Inflammation’ is the term used to describe a complex bodily response to damage. The word is derived from the Latin words meaning ‘to set on fire’, because two manifestations of inflammation are heat and redness. Two other important features are swelling and pain. These characteristics of inflammation have been familiar to doctors over many centuries. They were noted by the 1st century Roman medical encyclopaedist Celsus as calor (heat), tumour (swelling), rubor (redness), dolor (pain).

Inflammation has one other major characteristic in that it leads to ‘loss of function’ of the affected body part. Swelling and pain largely contribute to this loss of function. In mild disease, loss of function can be beneficial, as it encourages the patient to rest the inflamed area, and this should promote healing. For example, inflammation of the voice box (laryngitis) may give rise to discomfort and malaise. This means that the patient avoids talking, and may wish to rest in bed. Both these responses will promote healing.

In severe disease, the loss of function can jeopardise the health of the whole body, and is not necessarily so beneficial. For example, inflammation of the lining of the brain resulting from bacterial infection (meningitis) leads to swelling of the brain and carries the risk of coma and death.

The five characteristics of inflammation are listed in the Table 2.2b-I.

Table 2.2b-I The characteristics of inflammation

When a body part is inflamed, it is often medically described by the suffix ‘-itis’. This suffix may be added on to the common name for the affected organ or, more usually, to the Latin term for the organ. Hence in tonsillitis, dermatitis, laryngitis, osteomyelitis and tendonitis we would expect to find inflammation of the tonsils, skin, larynx, bone marrow and tendons, respectively (see Q2.2b-1)image.

The trigger for inflammation is always tissue damage. When tissues are damaged, cells are ruptured and release their contents. The presence of cell contents in the extracellular space has a powerful effect on the immune system and the capillary cells. The released chemical contents of cells signal to the immune system and capillary cells that there is cell debris that needs removing, that repairs may need to be performed, and that there might be foreign bodies and infectious organisms to be eradicated. Their presence induces responses in immune and epithelial cells that bring about the inflammatory response, and thus begins the process of healing. The chemicals released include the prostaglandins, histamine, serotonin (5HT) and bradykinin.

The purpose of inflammation in the body is protective. It enables isolation and inactivation of foreign material and damaged tissue, and leads to its removal from the body.

Some of the changes that occur in inflammation are summarised in Figure 2.2b-I.

Chronic Inflammation

The resolution of inflammation may be hindered by a poor blood supply, the presence of a foreign body or as a response to certain organisms. In the case of chronic inflammation, after a time increasing numbers of lymphocytes get attracted to the area and the scar-tissue forming cells, the fibroblasts, are continually activated meaning excess scar tissue may be formed. The chronic skin ulcer described in Chapter 2.1b is an example of chronic inflammation. Tuberculosis (TB) is an example of an infection in which the slow-growing infectious organism Mycobacterium tuberculosis encourages a chronic inflammatory response and the formation of clusters of immune cells around foci of infection known as granulomas (see Q2.2b-4)image. These tiny clusters of immune cells are characteristic of this disease and are evidence to the pathologist of its ability to induce damaging chronic inflammation.

Pathology of inflammation

Boils and abscesses

Boils and abscesses occur when excess pus is formed and collects within the tissues at a site of inflammation. Abscesses are simply big boils; there is no clear-cut difference between the two. Pus is more likely to collect if a foreign body is present at the site of inflammation and also if certain ‘pyogenic’ organisms are present. The most common pyogenic organism to cause medical problems is Staphylococcus aureus, one of the many normal and healthy (commensal) skin bacteria.

Pus is a problem because it is a reservoir of microbes, and thus a source of chemicals that act as pyrogens (i.e. lead to fever and malaise), and it inhibits full resolution of the inflammation.

A boil or abscess ideally heals by means of discharge of pus to the surface. For example, a stye (a boil of the edge of the eyelid) usually comes to a point after a few days and this then breaks open to release the pus and allow healing.

This ideal outcome is not always achieved. In some cases the pus does not discharge fully, and the channel leading from the pus to the skin does not heal fully, remains as a sinus that discharges pus long term. This can lead to long-term ill-health, as the body is always in a state of fighting infection. An infection in bone (osteomyelitis) can easily lead to sinus formation, because the bone is relatively protected from the immune system and thus chronic inflammation can easily develop in bone. This is a particular problem with shrapnel wounds in wartime, which may lead to a continual discharge of pus from the bone through a sinus to the skin.

When a sinus is formed, the discharge of pus can go two ways: into closely apposed organs (e.g. stomach and bowel, or bladder and bowel) so that a permanent channel is formed between them (fistula). This can have severe consequences. One common cause of a fistula is the inflammatory bowel disease Crohn’s disease. Diverticulitis of the bowel is another cause.

If the pus is not discharged at all it is eventually phagocytosed. This is a common occurrence with small boils (pustules) such as occur in severe acne. Instead of discharging fully, these form tender lumps that gradually become less painful. This form of healing is more likely to lead to scarring resulting from chronic inflammation, as fibrous tissue is formed to fill the cavity formed by the pus, and this can have severe cosmetic consequences (see Q2.2b-5)image.

The most appropriate medical treatment of boils and abscesses promotes natural resolution. Astringent medication in the form of hot packs (poultices) can be applied to the site of a superficial abscess to encourage the pus to discharge outwards.

Resolution can be assisted surgically by lancing, where a clean wound is made in the skin to allow natural drainage of the pus. A larger abscess may be drained by inserting a sterile

Oct 3, 2016 | Posted by in MANUAL THERAPIST | Comments Off on Processes of disease
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