Myasthenia gravis （MG） is an autoimmune disease of transmission dysfunction at neuromuscular junction， characterized by skeletal muscle fatigue， aggravated symptoms after activity， and mild symptoms in the morning and severe symptoms in the evening. Systemic sclerosis （SS） is also an autoimmune disease and often has Raynaud's phenomenon as the first symptom， accompanied by the manifestations such as skin swelling and sclerosis， joint pain， muscle weakness， and visceral organ involvement. Limited cutaneous SS is a subtype of SS， in which skin lesions are mainly confined to the distal end of the elbow （knee）， but it can also involve the skin on the face and neck， and it generally has slow progression. MG is often comorbid with other autoimmune diseases such as hyperthyroidism， systemic lupus erythematosus， rheumatoid arthritis， and pemphigus， but MG comorbid with SS is rare in clinical practice. This article reports a case of MG comorbid with SS. Two years after the diagnosis of MG， the patient developed symptoms such as skin hardening and thickening on the face and extremities， skin becoming purple at the distal ends of the extremities when it was cold， and chest distress. No special treatment was given during this period， and later the patient was admitted due to aggravation of symptoms. The patient was diagnosed with limited cutaneous SS， MG， pulmonary hypertension， chronic cardiac insufficiency， and pulmonary infection based on auxiliary examination results and clinical manifestations. During hospitalization， the patient was treated with methotrexate for immunosuppression， as well as prednisone acetate and pyridostigmine bromide for myasthenia， pulmonary hypertension， heart failure， and infection， but finally， the patient died of septic shock. This article summarizes the clinical data and characteristics of the patient， reviews related articles， discusses the pathogenesis and pathogenic characteristics of the two diseases， and analyzes the possible relationship between the two diseases and the problems that should be taken seriously in the course of diagnosis and treatment， in order to provide suggestions and references for clinical work.