Stiff Person Syndrome in a patient with atypical carcinoid tumor of the lung secondary to anti-amphiphysin antibodies: A case report and literature review

Background: Stiff Person Syndrome (SPS) is a rare neurological disorder of unclear etiology characterized by two set of symptoms; skeletal muscle stiffness and rigidity primarily affecting the truncal musculature due to continuous co-contracture of agonist and antagonist muscles, and superimposed episodic spasms axial rigidity, limb stiffness, difficulty walking, and postural instability. SPS is classified into classic SPS, paraneoplastic SPS, and SPS variants- that include segmental SPS, Jerky SPS, Progressive encephalomyelitis with rigidity and myoclonus, and SPS plus syndrome. Case report: we present the first reported case of SPS in association with atypical lung carcinoid in a 48-year-old male patient. He was diagnosed with SPS based on the progressive muscle stiffness and the amphiphysin antibody seropositivity in the setting of known atypical carcinoid Conclusion: This unusual case highlights the importance of keeping a high degree of suspicion for PSP when patients presents with typical symptoms in the sittings of known malignancy.