Linear psoriasis following the typical distribution of the sciatic nerve.

Background: Some studies suggest that the nervous system plays a role in the onset of psoriasis and psoriasis flares including the symmetry of lesions, sparing of denervated skin and the role of stress in inducing lesions.

Main observations: We describe an unusual case of psoriasis occurring in the same distribution as sciatic pain from a prolapsed intervertebral disc. The patient, a 45-year-old man with plaque psoriasis was treated with ustekinumab for 104 weeks, at a standard dose. During the eight month of therapy he developed an asymptomatic linear eruption on the left lower extremity along the distribution of the sciatic nerve. On examination, erythematous scaly plaques were noted. Histopathology confirmed the diagnosis of psoriasis. The treatment was continued and clobetasol proprionate 0.05% cream was added. At week 12 after the eruption, the patient reported a pain radiating through the buttock and posterior left leg during jogging. Magnetic resonance imaging showed lumbar disc herniation with compression of the L5-S1 spinal nerve roots. The patient stopped running and the psoriasis spontaneously receded, in a slow but complete fashion, without any local treatment.

Conclusion: There is substantial evidence that nerves play a key role in the pathogenesis of psoriasis. We hypothesized that local TNF-alpha, neuropeptides and nerve growth factor, which are produced by nerve root compression, played a critical role in this case of psoriasis onset in an area of pain from a bulging lumbar intervertebral disc. To our knowledge, a correlation of psoriasis and nerve root compression has not been described previously.