Human in vivo phosphorus 31 magnetic resonance spectroscopy of psoriasis. A noninvasive tool to monitor response to treatment and to study pathophysiology of the disease.

Background: There is no objective laboratory technique to measure and to monitor disease activity in psoriasis.
Objective: We assessed the effectiveness of using phosphorus 31 (31P) magnetic resonance spectroscopy (MRS) to noninvasively monitor metabolism in psoriasis and to compare these spectroscopic data with chromatographic analysis.
Methods: Fourteen persons were enrolled in the study. 31P magnetic resonance spectra were obtained from skin of persons without skin disease, uninvolved psoriatic skin, nonpsoriatic erythroderma, and from skin of patients with psoriasis. In three patients with psoriasis 31P magnetic resonance spectra were repeated after treatment with methotrexate, UVB, etretinate, and topical steroids. Finally, shave biopsy specimens were obtained from two patients with psoriasis and submitted for chromatographic evaluation.
Results: In patients with severe psoriasis, in comparison with the control group, elevations in phosphomonoester concentrations and in the phosphomonoester/phosphodiester ratio were observed. These appear to be useful markers to monitor treatment response in patients with psoriasis. Finally, 31P MRS data in conjunction with chromatographic analysis indicated a defect in phosphometabolism in psoriatic skin. However, it is unclear whether this defect is a cause or an epiphenomenon of the disease.
Conclusion: 31P MRS appears to be a sensitive, noninvasive technique to monitor disease activity in psoriasis. Further studies to characterize the defect in phosphometabolism in psoriatic skin are warranted.