 Microscopy and culture (in modified Kelly's medium) of skin biopsy or blood samples.The course of ACA is long-standing, from a few to several years, and it leads to extensive atrophy of the skin and, in some patients, to the limitation of upper and lower limb joint mobility.The outlook is good if the acute inflammatory stage of ACA is treated adequately.The therapeutic outcome is difficult to assess in patients with the chronic atrophic phase, in which many changes are only partially reversible.