Bilateral Parsonage–Turner Syndrome in a Patient With Hemophagocytic Lymphohistiocytosis

<b>Introduction:</b> Parsonage-Turner syndrome (PTS), also known as idiopathic brachial plexopathy, is an uncommon peripheral neuropathy, and the presentation of bilateral PTS is even rarer. Hemophagocytic lymphohistiocytosis (HLH) is a hyperinflammatory disorder that is normally considered hematologic but can involve the nervous system in up to 70% of cases. <b>Case Presentation:</b> A 56-year-old Caucasian female with a history of SLE, rheumatoid arthritis, Sjogren's disease, and Hashimoto's thyroiditis, but no prior neurologic history, was admitted for the management of isolated thrombocytopenia, diagnosed with HLH, and then developed bilateral upper extremity pain, weakness, and numbness. A diagnosis of bilateral PTS was supported by magnetic resonance imaging (MRI) findings of mild symmetric increased enhancement in the bilateral shoulder muscles, and electromyography/nerve conduction study (EMG/NCS) revealed active denervation in the shoulder muscles bilaterally. The patient was started on methylprednisolone 1000 mg for three days, followed by a long steroid taper along with physical/occupational therapy with significant improvement of her symptoms. <b>Conclusion:</b> It is important to maintain a high index of suspicion for PTS in patients with new-onset shoulder or upper arm pain, weakness, and sensory deficits, even if findings are bilateral. Concomitant inflammatory disorders, infection, and recent surgeries/procedures should prompt a high degree of suspicion of this disorder, and the use of relevant diagnostics, such as MRI brachial plexus and EMG/NCS, should help guide diagnosis, as this condition is very responsive to treatment.