We report a patient with pustular psoriasis (Zumbusch type) with diffuse muscle pain. Evaluation of skeletal muscle metabolism during rest, graded levels of exercise and recovery was performed using 31phosphor magnetic resonance spectroscopy (31P MRS). Our results underline the systemic character of severe pustular psoriasis. The clinical improvement after drug therapy (prednisolone and etretinate) correlated well with the measurable changes in vivo of several metabolites and indices important in muscle contraction, such as phosphocreatine (PCr), inorganic phosphate (Pi), intramuscular pH and the phosphorylation potential (PCr/Pi). Abnormal accumulation of sugar phosphates (phosphomonoester) as well as their slow resolution during recovery reflect profound alteration of metabolism in the sense of block in glycolysis. Our results show that 31P MRS is well suited to identify and measure subtle changes in the muscle metabolism occurring in pustular psoriasis.