Many causes range from diabetes, autoimmune illnesses such as Sjogrens, and Lupus, previous chemotherapy, Ehlers-Danlos, Scleroderma, amyloidosis, and vitamin deficiencies such as copper and b12.
In nearly 1/3 of cases the cause is unknown but recent research is pointing to an “apparently autoimmune” cause in some with the recent discovery of TS-HDS and FGFR3 antibodies.