An observation of carcinoid syndrome in a woman of 47 suffering from malignant 
carcinoid of the ileum with metastases into the liver and right ovary is 
described. The clinical picture included diarrhea, heat waves, bronchospasms, 
hypertension, hyperserotoninemia, affection of the mitral valve and left atrium. 
"Carcinoid plaques" in the endocardium formed due to excessive proliferation 
under the influence of serotonin and kinins of polypotent subendothelial cells 
followed by their differentiation into fibroblast-like and smooth-muscle 
elements and production of basophilic interstitial substance. The receding 
rheumatic affection of the mitral valve may be the cause of the predominant 
involvement of the left part of the heart.