Autoimmune myositis （AIM） is a group of autoimmune diseases that primarily affect muscle fibers， often accompanied by the involvement of multiple organs such as the skin，lungs，and joints.It is the most common treatable skeletal muscle disease in adults. Although most patients with AIM can achieve remission with traditional immunosuppressive therapies， their quality of life can be heavily reduced due to drug-related adverse effects and the high relapse rate and high disability rate of the disease. With the deepening understanding of the immunopathological mechanisms of AIM，various biologics targeting different components of these mechanisms have brought new hope for patients with AIM. This article reviews the advances in the treatment of AIM.

Glycogen storage disease type Ⅱ （GSD Ⅱ）， also known as Pompe disease， is a common autosomal recessive lysosomal storage disease with predominantly muscle tissue involvement， and it is caused by defects in the GAA gene which encode acid α-D-glucosidase in lysosomes. According to the age of onset and the main organs involved， it is classified into infant-onset Pompe disease （IOPD） and late-onset Pompe disease（LOPD）. The diagnosis of this disease depends on the reduction in GAA enzyme activity， the detection of GAA gene mutations， and muscle tissue biopsy， and early diagnosis and treatment are crucial for prognosis. Recombinant human GAA（rhGAA） enzyme replacement therapy prepared by the gene recombination technology is currently the main disease-modifying treatment method for Pompe disease， among which the earliest drug alglucosidase α has shown good efficacy in improving muscle strength and respiratory function and prolonging survival time， and the new-generation rhGAA drugs avalglucosidase α and cipaglucosidase alfa provide new options， especially for patients with poor outcomes and severe symptoms. Substrate ablation therapy and gene therapy are still under exploration， and disease-modifying therapies combined with nutritional and exercise therapies and multidisciplinary long-term management will achieve twice the result with half the effort.
Diagnosis

Sporadic late-onset nemaline myopathy （SLONM） is a rare， acquired， and treatable myopathy with a subacute or chronic progressive clinical course， characterized by asymmetric muscle atrophy and weakness in the axial and limb muscles， with or without involvement of respiratory and cardiac muscles. The only definitive diagnostic method at present is the identification of rods accumulation in muscle fibers by muscle biopsy pathology. This article provides a review of the clinical manifestations， diagnostic evaluations， muscle pathology， and advances in the treatment of SLONM.
Immunotherapy

Lipid storage myopathy （LSM） is a lipid metabolic disorder characterized by excessive lipid droplet accumulation in muscle fibers. Classic multiple Acyl-CoA dehydrogenase deficiency （MADD）， also known as glutaric aciduria type Ⅱ， is a disease with various clinical manifestations caused by mutations in electron transfer flavoprotein （ETF） and ETF-ubiquinone oxidoreductase. In recent years， a large amount of evidence has shown that classic late-onset MADD caused by mutations in the electron transfer flavoprotein dehydrogenase gene is the main cause of LSM. Besides classic MADD， many other diseases with similar changes in blood acylcarnitines and urinary organic acids can also cause LSM， and such diseases are call MADD-like disorders or MADD spectrum. This article reviews the clinical， pathological， biochemical， and molecular features of LSM with various etiologies and the latest advances in treatment， with a focus on the latest findings associated with MADD spectrum.
Riboflavin

Mitochondrial diseases are a group of hereditary disorders characterized by impaired oxidative phosphorylation in the mitochondrial respiratory chain caused by defects in either mitochondrial DNA or nuclear DNA， and such diseases have complex and diverse clinical manifestations and often involve multiple organs and systems， with the main manifestation of lesions in the nervous system and muscles due to their high energy demands. At present， there is still a lack of effective therapies for most mitochondrial diseases， and therefore， multidisciplinary management is essential in clinical practice， integrating various therapeutic approaches to provide personalized treatment regimens for patients with mitochondrial diseases. The primary treatment principle involves the timely correction of pathological and physiological abnormalities through pharmacological interventions， dietary modifications， and exercise management， along with the prompt treatment of system-specific impairments and the prevention of potential complications.
Diagnosis

Objective:To summarize and discuss the clinical manifestations, muscle pathology and gene mutation characteristics of congenital myopathy with tremor and to improve clinicians′ understanding of the disease.Methods:The clinical data of a patient of congenital myopathy with tremor who visited Qilu Hospital of Shandong University in April 2021 were reported. Enzyme histochemical staining and immunohistochemical staining were performed on the muscle tissues of the patient, and the expression level of slow skeletal myosin binding protein-C (sMyBP-C) and mitochondrial DNA copy numbers were detected by Western blotting and quantitative real-time polymerase chain reaction. The literatures of congenital myopathy with tremor reported previously were reviewed and patients reported were summarized.Results:The proband is a 35 years old male, whose clinical symptoms occurred from childhood, mainly manifested as irregular muscle vibration of the limbs and exercise intolerance, with mild proximal limb muscle weakness. Muscle biopsy showed mild myogenic damage with abnormal mitochondrial changes, and gene detection showed MYBPC1 gene c.788T>G heterozygous mutation. Further detection showed that the expression level of sMyBP-C was significantly reduced, and the number of mitochondrial DNA copies was increased in the patient. The diagnosis of congenital myopathy with tremor was clear, and the symptoms did not progress during long-term follow-up. The clinical characteristics of 26 patients from this family and 10 families previously reported were summarized, and the results indicated that tremor was a prominent clinical manifestation of this disease, combined with mild to moderate muscle weakness, which could be accompanied with varying degrees of myasthenia, delayed gross motor development and skeletal joint malformation. The symptoms usually had no progress or chronic progress. Muscle biopsy usually indicated myogenic damage, including type Ⅰ fiber predominancy, type Ⅰ fiber atrophy and central cores in type Ⅰ fibers, which may be accompanied by mild mitochondrial abnormalities. The c.788T>G mutation in the MYBPC1 gene was a hotspot mutation of congenital myopathy with tremor. Conclusions:For early-onset tremor of unknown reason with muscle weakness, hypotonia, delayed gross motor development and skeletal joint malformation, it is necessary to consider the possibility of congenital myopathy with tremor, and to further perform electromyography, muscle biopsy, and gene detection for a clear diagnosis. Muscle biopsy usually indicates myogenic damage, and the c.788T>G mutation in the MYBPC1 gene is a hotspot mutation of the disease.

Pontine autosomal dominant microangiopathy and leukoencephalopathy (PADMAL) is an extremely rare autosomal dominant cerebral small vessel disease. Since the discovery of the pathogenic gene COL4A1, several PADMAL pedigrees have been reported in recent years. The pathogenesis of PADMAL is due to the increased formation of type Ⅳ collagen caused by mutation of the 3′ untranslated region of COL4A1. Abnormal accumulation of collagen in the extracellular matrix leads to thickening of the basement membrane and narrowing of the lumen. Patients present with recurrent lacunar infarction at early stage, and cognitive impairment may occur as the disease progresses. The main imaging changes of PADMAL are multiple lacunar infarcts and bilateral hemispherical white matter lesions. Under electron microscope, the lumen of small blood vessels in the skin is obviously narrowed and the basement membrane is thickened. Currently, there are no effective treatments or interventions for PADMAL.