Lung yin asthenia syndrome refers to syndrome of asthenic internal heat due to insufficiency of lung yin and failure of depuration. If internal disturbance of asthenic heat is not evident, it is called fluid consumption and lung dryness syndrome. This syndrome is mainly caused by consumption of lung yin due to dry heat impairing the lung or consumptive disease damaging the lung; or by consumption of fluid due to sweating; or by asthenia of lung yin due to chronic cough impairing lung yin.
 
Clinical manifestations:
Dry cough with scanty sputum, or scanty and sticky sputum difficult to expectorate, or sputum mixed with blood, hoarseness, dry mouth and throat, emaciation, feverish sensation over five centers (palms, soles and chest), afternoon tidal fever, flushed cheeks and night sweating, reddish tongue with scanty fluid as well as thin and fast pulse. These symptoms are seen in the rehabilitative stage of various infective diseases (such as pneumonia, bronchitis and whooping cough) as well as pulmonary tuberculosis, endobronchial tuberculosis, bronchiectasis and lung cancer, etc.
 
Analysis of symptoms:
Dry cough with scanty sputum or with scanty and sticky sputum difficult to expectorate is due to insufficiency of lung yin and internal generation of asthenic heat which deprive the lung of moisture and lead to adverse flow of qi; sputum mingled with blood is due to bleeding resulting from asthenic fire scorching the lung collaterals; hoarseness is due to insufficiency of lung yin, loss of proper moisture of the throat and fumigation of asthenic fire; dry mouth and throat and emaciation are due to insufficiency of lung yin and lack of nutrition; afternoon tidal fever, feverish sensation over the five centers, flushed cheeks, night sweating, reddish tongue with scanty saliva and thin and fast pulse are signs of internal heat due to yin asthenia.

Key points for syndrome differentiation:
Dry cough, scanty and sticky sputum and internal heat with yin asthenia.