Mirman, Igal

ABSTRACTBackground and AimsChronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is difficult to distinguish from mimicking disorders, with misdiagnosis resulting in IVIG overutilization. We evaluate a clinical‐electrophysiological model to facilitate CIDP versus mimic neuropathy prediction.MethodsUsing the European Academy of Neurology/Peripheral Nerve Society (EAN/PNS) 2021 CIDP guidelines we derived 26 clinical and 144 nerve conduction variables. The model was generated and validated utilizing total CIDP (n = 129) and mimics (n = 309); including (1) IgG4‐nodopathies; (2) POEMS (polyneuropathy–organomegaly–endocrinopathy–monoclonal protein‐skin changes); (3) anti‐myelin‐associated‐glycoprotein; (4) paraneoplastic; (5) Waldenström B‐cell lymphoma; (6) diabetic neuropathies; (7) amyloidosis; (8) Charcot–Marie–Tooth; (9) motor neuropathies/neuronopathies; and (10) idiopathic‐inflammatory‐myopathies.ResultsWe analyzed 9282 clinical and 51 408 electrophysiological data points. Univariate analysis identified 11 of 26 clinical variables with significant odds ratios. A multivariate regression model using four clinical and two electrophysiologic variables achieved 93% area‐under‐curve (95% CI 91–95): progression over 8 weeks (OR 40.66, 95% CI 5.31–311.36), absent autonomic involvement (OR 17.82, 95% CI 2.93–108.24), absent muscle atrophy (OR 16.65, 95% CI 3.27–84.73), proximal weakness (OR 3.63, 95% CI 1.58–8.33), ulnar motor conduction velocity slowing < 35.7 m/s (OR 5.21, 95% CI 2.13–12.76), and ulnar motor conduction block (OR 13.37, 95% CI 2.47–72.40). A web‐based probability calculator (https://news.mayocliniclabs.com/cidp‐calculator/) was developed, with 100% sensitivity and 68% specificity at a 92% probability threshold. Specificity improved to 93% when considering “red flags,” electrophysiologic criteria, and laboratory testing.InterpretationA probability calculator using clinical electrophysiological variables assists CIDP differentiation from mimics, with scores below 92% unlikely to have CIDP. The highest specificity is achieved by considering clinical “red flags,” electrophysiologic demyelination, and laboratory testing.

Abstract Objectives Mutations in VCP, HNRNPA2B1, HNRNPA1 , and SQSTM1 , encoding RNA‐binding proteins or proteins in quality‐control pathways, cause multisystem proteinopathies (MSP). They share pathological findings of protein aggregation and clinical combinations of inclusion body myopathy (IBM), neurodegeneration [motor neuron disorder (MND)/frontotemporal dementia (FTD)], and Paget disease of bone (PDB). Subsequently, additional genes were linked to similar but not full clinical‐pathological spectrum (MSP‐like disorders). We aimed to define the phenotypic‐genotypic spectrum of MSP and MSP‐like disorders at our institution, including long‐term follow‐up features. Methods We searched the Mayo Clinic database (January 2010–June 2022) to identify patients with mutations in MSP and MSP‐like disorders causative genes. Medical records were reviewed. Results Thirty‐one individuals (27 families) had pathogenic mutations in: VCP ( n = 17), SQSTM1 + TIA1 ( n = 5), TIA1 ( n = 5), MATR3, HNRNPA1, HSPB8 , and TFG ( n = 1, each). Myopathy occurred in all but 2 VCP ‐MSP patients with disease onset at age 52 (median). Weakness pattern was limb‐girdle in 12/15 VCP ‐MSP and HSPB8 patient, and distal‐predominant in other MSP and MSP‐like disorders. Twenty/24 muscle biopsies showed rimmed vacuolar myopathy. MND and FTD occurred in 5 (4 VCP , 1 TFG ) and 4 (3 VCP , 1 SQSTM1 + TIA1 ) patients, respectively. PDB manifested in 4 VCP ‐MSP. Diastolic dysfunction occurred in 2 VCP ‐MSP. After 11.5 years (median) from symptom onset, 15 patients ambulated without gait‐aids; loss of ambulation ( n = 5) and death ( n = 3) were recorded only in VCP ‐MSP. Interpretation VCP ‐MSP was the most common disorder; rimmed vacuolar myopathy was the most frequent manifestation; distal‐predominant weakness occurred frequently in non‐ VCP ‐MSP; and cardiac involvement was observed only in VCP ‐MSP.