Chronic Inflammatory Demyelinating Polyradiculoneuropathy (CIDP) as a presentation of Familial Amyloid Polyneuropathy (FAP): diagnostic error or overlap?

Case report: Male, 72 years old, with progressive tetraparesis, paraesthesia and burning pain with distal predominance. Electroneuromyography (ENMG) showed findings suggestive of sensory-motor axonal polyneuropathy and signs of active and chronic denervation in the L5 and S1 territory. Underwent lumbar arthrodesis and during surgery, presented symptomatic bradycardia requiring a pacemaker. He reported partial pain improvement, but had bilateral foot drop and bladder retention. New ENMG demonstrated findings, now suggestive of CIDP. Underwent intravenous corticosteroid therapy without improvement. In 2019, he presented dysphagia for solids, weight loss, erectile dysfunction, postural hypotension and sensory-motor worsening. Underwent Human Immunoglobulin for 6 months. As there was no improvement, he was referred to our service. Best analysis in history revealed heart disease in 3 siblings. Genetic sequencing was performed for FAP that demonstrated a VAL50MET mutation. Context: FAP is an autosomal dominant inherited disease, caused by mutations in the transthyretin (TTR) gene that determine the accumulation of abnormal protein aggregates. Peripheral neuropathy differs from classic CIDP pattern by the distribution of weakness, important impairment of fine fibers and refractoriness to immunosuppressive treatment. Conclusions: FAP is a serious and treatable condition. Early diagnosis has a huge impact on life quality. Although confusion with CIDP is frequent, it is possible through history to differentiate these conditions.