Prevalence of Charcot-Marie-Tooth (CMT) Disease and chronic inflammatory demyelinating polyneuropathy (CIDP) are each reported between 1-20 per 100,000 individuals. Co-occurrence of these entities is not well delineated in current literature. We report 3 pediatric cases of genetically confirmed neuropathy and coexisting CIDP.

Case #1: 6-year-old girl developed progressive weakness. Exam showed areflexia. CSF protein was 99mg/dL. MRI revealed thickened, enhancing nerve roots. Electrodiagnostics demonstrated conduction block. She partially improved after methylprednisolone and intravenous immunoglobulin (IVIg). Her and her symptomatic sister’s genetic testing showed homozygous SH3TC2 variants of unknown significance, consistent with CMT4c. Her distal predominant weakness continued, with subacute worsening after IVIg tapers. 

Case #2: 5-year-old boy developed subacute difficulty walking. MRI showed nerve root enhancement. He improved after IVIg, but with fluctuating weakness, worse after sports injuries. Electrodiagnostics later showed prolonged F-waves and chronic neurogenic changes. Genetics testing revealed a PMP22 deletion, consistent with hereditary neuropathy with liability to pressure palsies (HNPP).

Case #3: Infant with hypotonia and weakness. Exam at 16-months-old showed generalized weakness, decreased bulk, and areflexia. Electrodiagnostics revealed diffuse sensorimotor polyneuropathy. Muscle and nerve biopsies exhibited neurogenic atrophy, axonopathy, demyelination, and endoneurial fibrosis. Genetics testing showed a pathogenic MPZ mutation, consistent with CMT3. Weakness progressed, but incidentally improved after methylprednisolone was given for acute illness. CSF protein was 124/dL, with elevated IgG and IgG synthesis. He improved slightly after IVIg and methylprednisolone.

This series discusses three patients with both genetic polyneuropathies and CIDP. Although these children had mutations explaining underlying weakness, they had diagnostics, such as nerve root enhancement, cytoalbuminologic dissociation, elevated CSF IgG, not explained by genetic syndromes. This series suggests that myelin related gene mutations may predispose patients to acquired polyneuropathies, and highlights the importance of comprehensive work-up, as some neuropathies are treatable but only demonstrate partial improvement alongside co-occurring genetic polyneuropathy.