BACKGROUND: Psoriasis on the oral mucosa is not often diagnosed by practicing dentists, as it occurs in 23% of patients. Various factors are of primary importance in the occurrence and development of this pathology. AIM: This study aimed to present a clinical case of psoriasis lesions in the oral mucosa to determine a set of interdisciplinary diagnostic and therapeutic measures for combined lesions of the skin and oral mucosa in patients with psoriasis. MATERIAL AND METHODS: Changes in the mucous membrane of the tongue in a patient with psoriasis vulgaris is described. The manifestations in the oral cavity were identified as ICD-10-L40.0X. RESULTS: A combination of diagnostic and therapeutic measures is presented with simultaneous manifestations of the disease on the skin and in the oral cavity. CONCLUSION: The presented clinical example demonstrates the need for a comprehensive interdisciplinary examination and consultation with doctors of different specialties. For differential diagnosis and determination of the disease course, prognosis, and main research methods, it is necessary to perform histological examination of the biopsy of the pathological site of the oral mucosa, and if necessary the skin, and autofluorescence stomatoscopy of the oral mucosa and tongue. The described diagnostic and therapeutic measures will contribute not only to stopping the disease recurrence but also to reducing the level of stress, carcinophobia, and thereby improve the quality of life of the patients.