RESUMO
BACKGROUND: The etiology of POEMS syndrome and its associated polyneuropathy have not been fully elucidated. The clinical picture of POEMS-associated polyneuropathy and nutritional polyneuropathy due to vitamin B6 (VB6) deficiency are strikingly similar, both being typically sensorimotor, symmetrical, stocking and glove distribution, and more severe in the lower extremities. CASE PRESENTATION: We report two consecutive POEMS patients with VB6 deficiency who showed unusual rapid and drastic recovery of polyneuropathies within 6-8 weeks after oral VB6 supplementation. Case 1 was supplemented with VB6 from time of autologous stem cell transplantation. Polyneuropathy began to improve within one week, and he became walker-free and could walk unaided with a cane within 6 weeks. Case 2 was supplemented with VB6 from time of stem cell harvest, and he became cane-free and his gait almost normalized within two months. Nerve conduction studies were also confirmatory of neurologic recovery in both cases. CONCLUSIONS: Objective physical improvement of POEMS-associated polyneuropathy has been reported to typically require approximately a year after autologous stem cell transplantation, and together with our observations of VB6 deficiency and supplementations leading to accelerated recoveries of polyneuropathy, VB6 deficiency most probably contributes to POEMS-associated polyneuropathy. VB6 acts as a coenzyme in approximately 150 biochemical reactions. VB6 has been reported to inhibit the hypoxia-inducible factor/vascular endothelial growth factor (VEGF) pathway, and VEGF levels are known to corollate with disease activity of POEMS syndrome. Therefore, VB6 deficiency may contribute not only to POEMS-associated polyneuropathy, but also to the etiology of POEMS syndrome itself.