Biotin, also known as vitamin B8 and vitamin H, is a water-soluble sulfur-containing vitamin that, like other B vitamins, is mostly consumed in food and, to a lesser extent, synthesized in bacteria in the body’s intestinal tract. Biotin is widely found in natural foods, with high content in animal liver, soybean, egg yolk, fresh milk and yeast, but little in grains, vegetables, fruits and meat. Biotin is a coenzyme of mitochondrial propionyl coenzyme A carboxylase, pyruvoyl carboxylase, acetyl coenzyme A carboxylase and methyl crotonyl coenzyme A carboxylase, and is involved in the metabolism of three major nutrients, namely carbohydrate, protein and fat, as a cofactor of carboxylation, decarboxylation and dehydrogenation enzymes. Biotin deficiency leads to decreased activity of four related carboxylases and impaired mitochondrial energy synthesis, resulting in metabolic acidosis, organic aciduria, and a series of neurological and dermatological damages, which can be fatal in severe cases. Biotin is also an important active substance in DNA synthesis, which is involved in cell repair and regeneration. The clinical manifestations of biotin deficiency are mainly skin, mucous membrane and neurological damage. In the general population, long-term biotin deficiency may cause damage to hair, nails and skin, such as eczema, hair loss, dry skin, peeling, keratitis, oral ulcer, tongue inflammation, conjunctivitis, keratitis, perineal inflammation, psoriasis, and in severe cases, neuropsychiatric damage such as loss of appetite, weakness of limbs, paralysis, ataxia, convulsions, depression, demyelination, optic nerve atrophy, vision and hearing loss, etc. The deficiency of biotin can also cause cellular immunity and immune system disorders. Biotin deficiency can also cause a decrease in cellular and humoral immune function, and patients are often combined with Candida and bacterial infections. 3.Treatment and prognosis of biotin deficiency Biotin supplementation therapy is effective for biotin deficiency patients, with a general dose of 5-40 mg/d. After a few days, the abnormal urinary metabolites disappear and the general condition improves significantly. Patients with biotin deficiency can have normal biotin levels after short-term biotin supplementation, diet and lifestyle modifications. Patients with biotinase deficiency require lifelong biotin supplementation. In children with severe biotinase deficiency, protein restriction, glucose supplementation and correction of acidosis are also required in case of metabolic acidosis or hyperammonemia. In order to improve the survival rate and quality of life of children, in addition to the active introduction of relevant diagnostic and therapeutic techniques, it is necessary to raise awareness and conduct early etiological analysis of suspected children for early detection and early treatment. In some countries, newborn screening for this disease is carried out in order to achieve prediagnosis. In China, some institutions have implemented high-risk screening for this disorder using gas chromatography-mass spectrometry (GC-MS) for urine organic acids and tandem mass spectrometry (MS) for blood esteryl carnitine spectrometry.