A Pilot Study of Technetium [99Tc] Methylene Diphosphonate in the Treatment of Psoriatic Arthritis

Inclusion Criteria: * 18-70 years of age; * Clinical diagnosis of PsA according to the CASPAR classification criteria * Active PsA at baseline defined as ≥ 3 tender joints and ≥ 3 swollen joints * If subjects were taking csDMARDs, the doses of csDMARDs had to be stable for at least 4 weeks and had to remain the same during the trial * The application of bDMARDs and tsDMARDs should meet the following requirements: 1. Etanercept and its biological analogues: stop at least 4 weeks prior to their baseline visit; 2. Other biological: stop at least 6 months prior to their baseline visit 3. tsDMARDs: stop at least 8 weeks prior to their baseline visit * If subjects were taking glucocorticoids, the doses of GC(prednisone \< 10mg) had to be stable for at least 4 weeks and had to remain the same during the trial; * Non steroidal anti-inflammatory drugs: if applied, the dose was stable one week prior to their baseline visit * Negative pregnancy test for child-bearing women at screening and baseline * Provide written informed consent Exclusion Criteria: * Patients with severe heart, liver, kidney and other important organ diseases * Abnormal liver function (ALT or AST is 2 times higher than normal) * White blood cell count less than 4,000/mm\^3 (less than 4 X 10\^9/L) * Platelet count less than 100,000/mm\^3 (less than 100 X 10\^9/L) * Serum creatinine more than or equal to 1.5 mg/dL (less than or equal to 132.6 μmol/L) * Pregnancy or breastfeeding women * Contraindications to 99Tc-MDP therapy and/or known hypersensitivity to 99Tc-MDP * Participated in other drugs clinical trials within 4 weeks