Objective To analyze the clinical evolution of a patient affected by Alzheimer's disease and discuss the repercussions of an early diagnosis. Method Instrumental case study of qualitative and descriptive type that was developed in three stages: 1) selection and delimitation of the case; 2) collection of data in the field; and 3) organization and writing of the report. This study is based on the analysis of the clinical evolution described in the medical records of a patient diagnosed with Alzheimer's disease, treated and followed-up by the Center for Psychosocial Care (CAPS), for a period of 10 years, in the Alto Vale do Rio do Peixe region. Results This study was conducted with the patient M.R., female, 71 years old, married, housewife, with incomplete elementary education, carrier of AD and hypothyroidism, who started her follow-up at CAPS II on September 10, 2012. Patient submitted to the Mini Mental State Examination (MMSE), with a result of 14 points in the first test, below the cut-off point for the patient's level of education. Later, in 2018, she scored 10 points on the MMSE, and in 2020 she scored 11, already under medication treatment for AD: memantine 10mg 2x/day and donepezilla 5mg 1x/day. Conclusion Early diagnosis of AD is extremely important for appropriate treatment to slow the progression of the disease. However, mental disorders such as depression are barriers in the initial clinical analysis of patients and in some cases presents itself as a prodrome for AD.