By Gary M. White, MD
Multilevel Symmetric Neuropathic Pruritus (MSNP) is a recently described condition of diffuse itch of neuropathic origin, seemingly related to degenerative disc disease (DDD).
An older patient presents with diffuse symmetric itch of the trunk, arms and legs. There is no primary skin lesion, but there may be excoriations or prurigo nodules from scratching.
Asking the patient to delineate the areas that itch with a pen can be very helpful. In MSNP, the patient will tend to mark symmetric and localized areas. Thus, verifying one key feature of MSNP. That is, the itch is fixed and localize to distinct areas---not variable nor generalized.
Imaging shows DDD.
Workup to exclude other causes of pruritus may include CBC, metabolic panel, thyroid stimulating hormone, medication review and complete spinal imaging.
A more advanced workup could include, depending upon clinical indications, serum IgE, bullous pemphigoid antigens, tissue transglutaminase, HIV, age and sex-appropriate cancer screenings, CXR, skin biopsy for direct immunoflourescence, patch testing and brain CT.
Gabapentin (300-1200 mg/day) can be dramatically helpful. Occasionally, the antidepressant mirtazapine (7.5-15 mg at bedtime) can be given for nighttime pruritus.
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