Symmetrical flaccid paralysis of the extremities, or periodic paralysis, is a group of muscle disorders characterized by periodic episodes of delayed paralysis mostly associated with abnormal potassium metabolism, with hypokalemic periodic paralysis being the most common. The clinical features are recurrent episodes of flaccid paralysis or weakness of skeletal muscles lasting from a few hours to a few weeks, with interictal periods of normalcy. In some cases, there is a family history. If hyperthyroidism, nephropathy or other metabolic diseases are present, the paralysis is secondary to periodic paralysis. Differential diagnosis of symmetrical limb flaccidity: 1. primary aldosteronism There are often recurrent episodes of limb weakness and hypokalemia, but the age of first onset is older, the duration of each episode can last for several months, and the symptoms are slow to resolve and often do not easily return to normal; in addition, there are also features such as increased blood pressure and nocturia. 2, acute infectious polyneuritis Most patients have a history of upper respiratory or gastrointestinal tract infection for several days to weeks before the disease, and the symptoms gradually worsen after the onset of the disease, reaching a peak within 1 to 2 weeks, and start to recover 2 to 4 weeks after the condition is stabilized, and the cerebrospinal fluid examination can reveal the phenomenon of protein cell separation; while periodic paralysis episodes reach a peak or recovery time is shorter, accompanied by a decrease or increase in serum potassium, generally not accompanied by obvious The episodes of periodic paresis have a shorter time to peak or recover, with reduced or increased serum potassium, and are generally not accompanied by significant hyperalgesia. 3, myasthenia gravis is characterized by generalized partial or total skeletal muscle pathology with easy fatigue, aggravated by activity and improving after rest, effective for cholinesterase inhibitors, 90% of patients have positive AchR-Ab in blood. 4.Acute barium poisoning There may be tetraplegia, droopy eyelids, difficulty in pronunciation and swallowing, as well as gastrointestinal symptoms such as muscle tremor, nausea and vomiting, diarrhea, and a history of eating salt or drugs containing too much barium. 5, polymyositis slow onset, with fever, muscle pain, Raynaud’s phenomenon, increased blood CPK, the duration of which is rarely shorter than a few weeks or months. 6, hypokalemic molluscumosis Most often occurs in cotton-producing areas and patients with a history of eating raw cottonseed oil, in addition to episodes of limb weakness, often accompanied by gastrointestinal symptoms, effective for potassium chloride treatment. 7, hyperthyroidism combined with hypokalemic periodic paralysis With clinical manifestations of hyperthyroidism, T3 and T4 are elevated, and periodic paralysis stops after normal thyroid function.