[The significance of hot spots in psoriatic skeletal involvement]

Bone scintigraphy is a modern method of low specificity but very high sensitivity in determining early changes in bone metabolism. There is a relationship between excessive skeletal metabolic disorders of the bone and the appearance of foci of maximum radionuclide uptake, or "hot spots". This distribution of radionuclide uptake has a specific character. In a retrospective study, we investigated the distribution of hot spots in 92 patients with various forms of psoriatic disease. Hot spots were found at and near to joints only. In enthesopathies hot spots are not found, because of lack of substance. They do, however, show signs suggesting a major disorder in collagen metabolism. Hot spots indicate a rather acute degree of skeletal involvement in psoriatic disease and are also frequently found in very active phases of psoriatic disease. Therapy-induced regression is possible. Spontaneous regression was observed only in the case of hot spots of short duration. The correlation of scintigraphic findings with X-rays shows that hot spots are signs of maximal focal metabolic activity. In a high percentage of cases they are leading up to a state of destruction, which can be shown on X-rays later. Among other parameters, they indicate the likelihood of skeletal involvement in psoriatic disease. Moreover, they indicate a high risk of "psoriatic arthritis".