[Internal medicine, seen from the mouth].

Many diseases affect the oral cavity. Therefore, the mouth is an organ that internists should observe carefully. Hereafter we present five illustrations of oral semiology that reflect a systemic condition: a strawberry tongue, an ulceration, a labial lesion, a gingival hyperplasia and a gingival hyperpigmentation. Each time, a differential diagnosis is to be considered, potentially allowing the identification of severe diseases.