Pediatric atrophy-flaccidity disease refers to a condition in children characterized by weakness of the limbs and inability to move voluntarily, with the lower limbs being more commonly affected in clinical practice.

Pediatric atrophy-flaccidity disease is referred to as "atrophy-flaccidity" in Suwen.Wei Lun; later generations have also called it "pestilent flaccidity of foot" or "soft wind." Due to its pestilential nature, it is also known as "pestilent flaccidity." Modern medical practitioners believe that the "half-body paralysis of small body" described in Yilin Gaicuo closely resembles this condition.

This condition is most commonly seen in children under 5 years old, with the highest incidence occurring between 1-2 years of age, and it often occurs in summer and autumn. This condition differs significantly from adult "limb flaccidity" in terms of age and seasonal onset.

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1. Initial Invasion of Dampness-heat, Pathogen Attack︰Pain and soreness in the limbs and muscles, difficulty in flexion and extension, skin hypersensitivity, aversion to being touched or held, or even neck stiffness, often accompanied by fever, sweating, cough, runny nose, nausea, vomiting, dysphoria or somnolence, loose stools, yellow urine, thin and greasy tongue coating, and soggy rapid pulse. This is caused by external contraction of wind-dampness-heat epidemic toxin and internal damage from unclean or cold food. The lungs, as the organs of clear purification, govern the skin and hair of the body. When epidemic toxin attacks externally, lung qi becomes depressed and obstructed, leading to disharmony between nutrient and defensive qi, resulting in exterior patterns such as fever and cough. Filthy turbid qi damages the spleen and stomach internally, preventing the clear qi from ascending and turbid qi from descending, hence manifesting interior patterns like vomiting and loose stools. Epidemic toxin invades the meridians, obstructing qi and blood circulation, and failing to dispel dampness-heat, causing tendon and vessel spasms, hence limb pain, skin hypersensitivity, or even neck stiffness. At the initial stage of epidemic toxin invasion, the disease belongs to an excess pattern. Treatment should focus on dispelling wind and releasing the exterior, clearing heat and draining dampness, supplemented by unblocking the collaterals. The recommended formula is Pueraria, Skullcap and Coptis Decoction combined with Sweet Dew Detoxicating Pill with modifications.
2. Dampness-heat Obstructing Collaterals, Qi Deficien︰The condition is primarily characterized by paralysis of the limbs, particularly asymmetric paralysis of the lower limbs. As the fever gradually subsides, the limbs become weak and flaccid, the skin feels cool, or there may be facial deviation. The tongue appears red with a greasy coating, and the pulse is fine and slippery. This occurs when healthy qi is unable to expel pathogens, or due to improper or delayed treatment, allowing dampness-heat pathogens to penetrate deeply into the meridians, leading to stagnation of yangming. The yangming governs the nourishment of all tendons and the binding of bones to facilitate joint movement. If dampness-heat stagnates internally without resolution, it inevitably results in deficiency of stomach qi, depriving the limbs of nourishment and causing the tendons to become slack and unable to support the bones. Consequently, muscle flaccidity and limb paralysis manifest. Dampness is heavy, turbid, and tends to descend, which is why paralysis of the lower limbs is particularly common. Treatment should focus on clearing heat and draining dampness, tonifying qi, and activating blood circulation. The recommended formulas are the Three Marvel Pill combined with the Yang-Tonifying Five-Returning Decoction. For cases with facial deviation, Pull Aright Powder should be added.
3. Evil Eliminated with Healthy Qi Weakened, Liver-ki︰Prolonged paralysis leads to muscle atrophy, cold skin, and even various deformities, characterized by paralysis, atrophy, weakness, looseness, coldness, and distortion. The tongue appears pale red with little or no coating, and the pulse is deep, thin, and weak. In prolonged paralysis, although the pathogenic factors have dissipated, the healthy qi fails to recover, especially due to the dual impairment of essence and blood, with liver-kidney depletion being the most severe. The liver governs the tendons, and the kidneys govern the bones. When essence and blood cannot nourish the tendons and bones, limb deformities appear. Muscles, deprived of nourishment, atrophy and lose their function. The treatment should focus on tonifying the liver and kidneys and warming and unblocking the collaterals. The recommended formula is Rehmannia Decoction with modifications. If there is deficiency of both yin and yang, with severe damage to qi and blood, it is necessary to greatly tonify qi and blood, as well as nourish the liver and kidneys. In such cases, Ten Major Tonics Decoction combined with Hidden Tiger Pill can be used with modifications.

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1. 《Pediatrics Zhengzhi Zhunsheng．Summer Heat Syndrome: "The spleen is the Taiyin, located in the Kun earth, prefers dryness and dislikes dampness. Therefore, those with insufficient spleen and stomach qi cannot lift clear yang and transport middle qi during the long, humid summer season. Additionally, during the time of Shaoyang ministerial fire, heat damages original qi, leading to sluggish limbs and weak legs."
2. Yilin Gaicuo．On Pediatric Hemiplegia: "This condition can occur from infancy to childhood. Sudden onset is rare; it mostly follows cold-damage disease, pestilence, smallpox, vomiting, and diarrhea. After illness, original qi gradually depletes, complexion turns pale, and gradually, limbs become immobile, even experiencing muscular spasms, with the body becoming like a clay sculpture, all due to qi not reaching the limbs."
3. Leijing．Volume Seventeen．Atrophy-Flaccidity Disease: "Treating flaccidity should focus on the Yangming, and also consider the affected meridians for combined treatment. For sinew flaccidity, treat the Ying and Shu points of Yangming and Jueyin; for vessel flaccidity, treat the Ying and Shu points of Yangming and Shaoyin; for fleshy flaccidity and bone wilting, the treatment is the same."