We present two cases of Hereditary Neuropathy with liability to pressure palsies (HNPP) misdiagnosed as chronic inflammatory demyelinating polyneuropathy (CIDP).

CIDP is frequently overdiagnosed. Key factors contributing to this error include incorrect electrodiagnostic interpretation, undue weight on subjective improvement after intravenous immunoglobulin (IVIG) therapy, and emphasis on cytoalbuminologic disassociation. HNPPs can mimic symptomology of CIDP and can fall victim to being misdiagnosed as one.

In the first case, a 69-year-old man presented with slowly progressive leg weakness and numbness.  He was diagnosed with CIDP at an outside practice 5 years prior to our evaluation and underwent IVIG therapy with mild subjective improvement. Our evaluation showed CSF protein was 90 and a chronic axonal sensorimotor neuropathy and severe entrapment neuropathy of the median nerve in our electrodiagnostic study. The physical exam noted high arched feet and hammer toes. Sural nerve pathology showed segmental demyelination with onion bulbs and large sized myelin reduplication. A subsequent genetic test found a deletion in PMP22, supporting a diagnosis of HNPP.  In the second case, a 62-year-old woman had trouble walking for years and had been diagnosed in 2021 with “Guillian-Barre” and treated with IVIG. Her CSF protein was 50. Symptoms transiently improved with IVIG but then worsened for years. Electrodiagnosis revealed evidence of chronic axonal sensorimotor neuropathy and entrapment neuropathy in the median and ulnar nerves across the pressure points. Sural nerve biopsy revealed segmental demyelination with onion bulbs and large sized myelin reduplication. A genetic test revealed a deletion in PMP22, supporting a diagnosis of HNPP.