This rare disorder may be Primary (cause unknown) It may also be secondary to Diabetes mellitus Gout Hypertension Lichen sclerosus Multiple sclerosis Myeloproliferative disorders (eg, polycythemia vera, thrombocythemia) Rheumatoid arthritis Spinal cord disorders Systemic lupus erythematosus Venous insufficiency Less commonly, the disorder is related to the use of some drugs (eg, nifedipine, bromocriptine).