Background Hoigné syndrome is the most common name given to a condition which has been called in different ways. Objective We want to show that an intralesional injection of prednisolone into the proximal nail fold may produce dorsal pain, dyspnoea and headaches within the 2 min following the injection and to explain the pathophysiology of his condition. Methods We studied the different drugs responsible for Hoigné syndrome by comparing the size of the crystals taking into account the diameter of pulmonary capillaries. The drug Company informed us that the size of the microcrystals were 2–4 μm vs. the 8 μm on average of the diameter of the pulmonary capillaries. Conclusion All the symptoms of Hoigné syndrome can be explained, especially the neuropsychiatric and neuropulmonary ones. Therefore, dermatologists should be aware of this phenomenon when they inject steroids in psoriatic nail patients.