625 - Expanding the Evidence: Chronic Inflammatory Demyelinating Neuropathy Following PCSK-9 Inhibitor Use

Case Diagnosis: Chronic inflammatory demyelinating polyneuropathy (CIDP) post Repatha injections

Case Description: A 76-year-old male with a history of hypertension, hyperlipidemia treated with PCSK-9 inhibitor Repatha due to statin intolerance and transient ischemic attack is referred for electrodiagnostic evaluation due to clinically unexplained weakness in the left limbs with pain and coordination issues that began shortly after receiving Repatha injections. He denies any alcohol or drug use and is currently taking acetaminophen, metoprolol, lisinopril, and aspirin. On physical exam, the patient exhibited decreased sensation to light touch below the left knee and to pinprick in the left posterior calf. There was also atrophy of the foot intrinsics. Electrodiagnostic studies were performed and indicative of demyelination and signs of possible axon loss with completed reinnervation and absence of motor units in the foot interossei.

Discussions: The electrodiagnostic findings showed a motor greater than sensory segmental demyelination peripheral polyneuropathy with possible axon loss and completed reinnervation. Based on the patient's history and the timing of the symptoms, along with a focused literature review, He was diagnosed with CIDP secondary to Repatha injections. Although not listed as an official side effect of Repatha, the patient reports several online anecdotal experiences, and there is one other case reported in the literature of PSCK-9 inhibitor-induced CIDP. This case resulted in similar findings to the previous literature but started with a different PSCK-9 Inhibitor, emphasizing that this may be an underrecognized adverse effect not limited to a specific medication or patient. It may be a side effect of the entire class warranting further studies into the prevalence among all PCSK-9 inhibitors.

Conclusions: Inflammatory neuropathy is not a well-documented side effect of PSCK-9 inhibitors. Patients should be monitored for clinical signs to guide early intervention and further research should be done into the prevalence of this side effect across the medication class.