Disclosures: Milan Ristic, DO: No financial relationships or conflicts of interest

Case Diagnosis: 37 year old female with left knee pain found to have sciatic schwannomatosis.

Case Description: Patient with complaints of knee pain with onset insidious 2 years ago and getting worse. Pain localized to her popliteal fossa, worse with palpation, worse with standing when seated for prolonged periods of time with occasional limping. Denied locking, clicking. Physical exam was significant for joint laxity, positive patellar grind, pain with deep squat, pes cavus, and increased Q angle. X-rays were unremarkable and she was sent to physical therapy for vastus medialis and vastus lateralis strengthening with primary diagnosis of patellofemoral syndrome.

Setting: Outpatient pain clinic.Assessment/

Results: Her pain worsened with therapy and a diagnostic ultrasound was significant for serpiginous hypoechoic masses with areas of vascularity. An MRI was done showing numerous well-circumscribed lobulated tumor masses along the course of the sciatic nerve, tibial and common peroneal nerves with a large cluster just above the knee joint anterior to the tibial and common peroneal nerves. She was referred to neurology and neurosurgery as well as a brain MRI and total spine MRI, genetic testing for LZTR1, SMARCB1 and NF2 which were unremarkable. She was started and uptitrated on Lyrica with mild pain relief and decision to take nonoperative management.

Discussion: In schwannomatosis, multiple noncancerous tumors grow on peripheral nerves with the most common symptom being chronic pain. It is usually cased by mutations in at least two genes (SMARCB1 and LZTR1) which act as tumor suppressors, along with somatic mutations in the NF2 gene or loss of chromosome 22.

Conclusion: Schwannomatosis can be the cause of chronic pain in select individuals. Despite negative genetic workup, some individuals may have the disorder in not already identified genes, most likely located on chromosome 22.

Level of Evidence: Level V

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PM&R Meeting Abstracts - https://pmrjabstracts.org/abstract/knee-pain-as-the-presenting-symptom-of-schwannomatosis/