Increased serum GDF15 has been reported also in other diseases affecting the peripheral nerves such as hereditary TTR amyloidosis,78 and Gdf15 gene expression is elevated in Garsmut CMT mouse models, where its induction was associated with activation of the integrated stress response.44 We therefore hypothesise that in CMT GDF15 is secreted to promote regeneration of peripheral neurons following nerve insult, which contributes to elevation of circulatory GDF15 in the serum. The gene discussed is GDF15; the disease is familial amyloid neuropathy.