This code system http://hl7.org/fhir/condition-category defines the following codes:

CodeDisplayDefinition
problem-list-itemProblem List ItemAn item on a problem list which can be managed over time and can be expressed by a practitioner (e.g. physician, nurse), patient, or related person.
encounter-diagnosisEncounter DiagnosisA point in time diagnosis (e.g. from a physician or nurse) in context of an encounter.