[Psoriasis arthropathica and seronegative rheumatoid arthritis--differential diagnostic considerations].

For differential-diagnostic considerations concerning seronegative arthritides two groups of patients with 25 patients each of the disease groups psoriasis arthropathica and serologically negative rheumatoid arthritis were selected. The differentiation of the two diseases was performed by clinical, paraclinical and radiological findings. When there are no typical psoriatic changes of skin and/or nails and there is an empty family anamnesis concerning this dermatosis, respectively, the coordination of seronegative arthritides is considerably rendered more difficult. Here the radiomorphological investigations particularly of the sacroiliacal joint and/or of the spine essentially contribute, since the arthritis of the sacroiliacal joint is to seen in high incidence in psoriasis arthropathica. Out of the number of the paraclinical values the determination of the complement factor C 4 and of immunoglobulin M gets the importance of a sign of differentiation, in which case C 4 in the psoriasis arthropathica and the immunoglobulin M in the seronegative rheumatoid arthritis are statistically significantly increased. The problems of the often difficult differential diagnosis between the two groups of disease can be clarified only by complex clinical examinations, paraclinical parameters and subtile radiodiagnosis. A close interdisciplinary cooperation between experienced dermatologists, rheumatologists and radiologists seems reasonable.