Etiology & Pathogenesis
The subject of Etiology is the study of the Causative Factors of diseases while the study of Pathogenesis concerns the processes whereby disease occurs, develops and changes within the body.
Numerous factors can cause disease and these include the Six Exogenic Factors, the Seven Emotions, improper diet, over/work or strain, lack of physical exercise, traumatic injuries, bites by insects or animals, as well as stagnant blood and phlegm fluid.
The symptoms and signs of any disease reflect the Pathological reaction of the body to certain causative factors. The causative factors therefore are studied both as the objective causes of disease and in the specific ways that they affect the body. On the basis of this understanding, Traditional Chinese Medicine (TCM) is able to identify the causative factors of disease by analyzing the clinical manifestations. This is know as "seeking the causative factors by differentiating symptoms and signs".
The study of Etiology therefore is based on developing a profound understanding of the characteristic of the clinical manifestations produced by each causative factor.
The Six Exogenous Factors -
(1)Wind is the predominant Qi of spring but may also occur in any of the four seasons. Wind may easily invade the body after sweating or during sleep.
a.Wind is the primary Exogenous Pathogenic Factor in causing disease since cold, dampness, dryness and heat all depend on wind to invade the body. Pathogenic wind cannot only combine with the other five Exogenous Factors but also with phlegm. Facial paralysis for example, is mostly seen as a consequence of the obstruction of wind phlegm in the meridians.
b.Wind is a Yang Pathogenic Factor and is characterized by upward and outward dispersion. Therefore it can easily invade the upper part of the body (i.e. the head, face and the exterior portion of the body) leading to impairment of the opening and closing of the pores. Clinical Manifestations are headache, nasal obstruction, itching or pain in the throat. Facial puffiness is an aversion to wind and sweating.
c.Wind in nature blows in gusts and is characterized by rapid changes. Disorders caused by Pathogenic wind therefore are marked by rapid changes in the migratory symptoms and abrupt onset of the disease known as "Wandering Bi Syndrome". Urticaria is caused by Pathogenic wind and is characterized by itching of the skin and wounds which appear and disappear from place to place.
d. Wind is characterized by constant movement. Moving Pathogenic wind in the body can cause dizziness, vertigo, fremitus, convulsions and opistotonos.
Cold is the Predominant Qi of water and may occur during other seasons but not as sever. Thin clothing, exposure to the cold after sweating, being caught in rain and wading in water in the winter can give rise to the invasion of Pathogenic cold.
a.Cold is a Yin Pathogenic Factor which consumes the Yang Qi of the body and as a result, the warming function of the body will be impaired. This results in symptoms such as cold limbs, cold pain in the epigastric and abdominal regions, diarrhea (containing undigested food) and increased flow of clear urine.
b.Cold is characterized by contraction and stagnation that results in the impairment of the opening and closing of the pores. As well as spasmodic contraction of the tendons and meridians causing impaired circulation of the Qi and blood. Accompanying symptoms include pain, aversion to cold, lack of sweating and restricted movement of the limbs.
(3) Summer Heat
Summer heat is the Predominant Qi of summer and unlike the other Exogenous Factors, is seen in its own season. Summer heat diseases are induced by high temperatures, over exposure to the sun or remaining for too long in poorly ventilated places.
a.Summer heat is characterized by extreme heat and is a Yang Pathogenic Factor which is transformed from fire. Clinical Manifestations characterized by Yang Heat including high fever, restlessness, thirst, profuse sweating and a surging pulse.
b.Summer heat is characterized by upward direction and the dispersion of body fluid while consuming large amounts of fluids. It usually affects the head and eyes which cause dizziness and blurred vision. Due to its dispersing function, Pathogenic summer heat may cause the pores to stay open accompanied by excessive sweating consuming body fluids resulting in thirst, dry mouth/tongue and scanty deep-yellow urine. Severe invasion of summer heat may disturb the mind resulting in sun stroke with the potential for sudden collapse and coma.
c.Since summer is often characterized by high humidity, Pathogenic summer heat is frequently combined with Pathogenic damp. Clinical Manifestations of summer heat and damp include dizziness, heaviness in the head, suffocating sensation in the chest, nausea, poor appetite, loose stools, general lassitude, fever, restlessness and thirst.
Damp is the predominant Qi of late summer - the period between summer and autumn. Many diseases related to the invasion by Pathogenic damp occurs at this time. Damp diseases may also be induced by living in damp conditions/places, wearing damp clothing due to sweat or rain, frequent exposure to water and periods of prolonged rain.
a.Damp is characterized by heaviness and turbidity. Patients often complain of dizziness, a heaviness sensation in the head (as though it were carrying a heavy load), soreness, pain and a heavy sensation in the joints. There may also be turbid discharges from the body such as suppurating sores, weeping eczema profuse purulent leukorrhea with a foul odor, turbid urine and stools containing mucus and even blood.
b.Damp is characterized by viscosity and stagnation. Patients affected by Pathogenic damp usually have a stubborn sticky tongue coating, a viscous stool that is difficult to excrete and obstructed urination. Diseases due to Pathogenic damp tend to be prolonged and interactable, such as fixed by "Bi Syndrome", damp fever (intestinal Typhoid) and eczema.
c.Damp is a Yin Pathogenic Factor which impairs Yang and easily obstructs the Qi circulation. Clinical Manifestations include a full sensation in the chest, epigastric distention, difficult/scanty urination and hesitant bowel movements with viscous stools. Since the spleen likes dryness and dislikes damp, Pathogenic damp is likely to impair the Spleen Yang leading to distention and fullness in the epigastric and abdominal areas, poor appetite, loose stools, reduced urination and oedema (due to poor transportation and transformation) and inadequate dispersion of body fluids.
Dryness is the predominant Qi of autumn.
a.Dryness consumes body fluid resulting in the dryness of the nose and throat, withered body hair, constipation and reduced urination.
b.Pathogenic dryness often impairs the function of the lungs, the "delicate Zang" (which has the function of dispersing, descending and moistening). Dryness invades the lungs through the nose or mouth. When the lack of moisture impares the dispersing and descending functions of the lungs and there maybe a dry cough with blood sputum.
(7) Fire (warmth and heat)
Fire, caused by the excess of Yang Qi often occurs in the summer but maybe seen in other seasons. Fire, warmth and heat vary in degree. Fire is the most severe and warmth the least severe, yet they all share similar characteristics. The terms of fire, heat and warm heat therefore are often used to describe their common features.
a.Fire is a Yang Pathogenic Factor characterized by burning and upward direction. Clinical Manifestations include high fever, restlessness, thirst, swelling, mouth and tongue ulcers, swollen/painful gums, headache, congestion of the eyes, insomnia and emotional excitement. Coma or delirium may occur if Pathogenic fire disturbs the mind.
b.Pathogenic fire often consumes Yin fluid. Burning Pathogenic fire heat can consume Yin fluid and force it to the exterior of the body. Apart from a high fever, there may be thirst, dry lips and throat, constipation and deep-yellow scanty urine.
c.Invasion by fire stirs up wind and causes disturbance of the blood. Excess of fire heat affects the liver meridian and deprives the tendons and meridians of nourishment, thus stirring up the liver wind. Clinical Manifestations include high fever, coma, convulsion of the four limbs, neck rigidity, opisthotonos and upward starring of the eyes. These symptoms are known as "Extreme Heat Stirring Up Wind".
7) The Seven Emotional Factors -
The Seven Emotional Factors in Traditional Chinese Medicine (TCM) are joy, anger, melancholy, worry, grief, fear and, fright. These are normal emotional responses of the body to external stimuli and do not normally cause disease. Severe continuous or abruptly occuring emotional stimuli however, which surpass the regulative adaptability of the organism will affect the physiological functions of the human body. This is especially when there is a pre-existing over sensitivity to them. The Qi and blood of the Zang Fu organs will be disrupted leading to disease. The Seven Emotional Factors, differing from the Six Exogenous Factors directly affect the Zang Fu organs, Qi and blood. They are considered to be the main causative factors of Endogenous Diseases.