* Trans-syndromal<unk> : coexistence, in a single patient, of two and/or more syndromes, pathogenetically related to each other. * Trans-nosological<unk> : coexistence, in a single patient, of two and/or more syndromes, pathogenetically not related to each other. The division of<unk>  as per syndromal and nosological principles is mainly preliminary and inaccurate, however it allows us to understand that<unk>  can be connected to a singular cause or common mechanisms of pathogenesis of the conditions, which sometimes explains the similarity in their clinical aspects, which makes it difficult to differentiate between nosologies. * Etiological<unk> : It is caused by concurrent damage to different organs and systems, which is caused by a singular pathological agent (for example due to alcoholism in patients suffering from chronic alcohol intoxication; pathologies associated with smoking; systematic damage due to collagenoses). * Complicated<unk> : It is the result of the primary disease and often subsequent after sometime after its destabilization appears in the shape of target lesions (for example chronic nephratony resulting from diabetic nephropathy (Kimmelstiel-Wilson disease) in patients with type 2 diabetes; development of brain infarction resulting from complications due to hypertensive crisis in patients suffering from hypertension). * Iatrogenic<unk> : It appears as a result of necessitated negative effect of the doctor on the patient, under the conditions of pre determine danger of one or the other medical procedure (for example, glucocorticosteroid osteoporosis in patients treated for a long time using systematic hormonal agents (preparations); drug-induced hepatitis resulting from chemotherapy against TB, prescribed due to the conversion of tubercular tests). * Unspecified (NOS)<unk> : This type assumes the presence of singular pathogenetic mechanisms of development of diseases, comprising this combination, but require a number of tests, proving the hypothesis of the researcher or physician (for example, erectile dysfunction as an early sign of general atherosclerosis (ASVD); occurrence of erosive-ulcerative lesions in the mucous membrane of the upper gastrointestinal tract in "vascular" patients). * "Arbitrary"<unk> : initial alogism of the combination of diseases is not proven, but soon can be explained with clinical and scientific point of view (for example, combination of coronary heart disease (CHD) and choledocholithiasis; combination of acquired heart valvular disease and psoriasis).
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