Post-ganglionic autonomic neuropathy associated with anti-glutamic acid decarboxylase antibodies

Antibodies to glutamic acid decarboxylase (GAD-Abs) have been associated with several conditions, rarely involving the autonomic nervous system. Here, we describe two patients complaining of autonomic symptoms in whom a post-ganglionic autonomic neuropathy has been demonstrated in association with significantly elevated serum and CSF GAD-Abs levels.

Patients underwent nerve conduction studies, sympathetic skin response testing, evaluation of autonomic control of the cardiovascular system and skin biopsy. Also, serum screening to exclude predisposing causes of peripheral neuropathy was performed. Anti-GAD65 antibodies were evaluated in serum and CSF.

GAD-Abs titer was increased in both serum and CSF in both patients. Sympathetic skin response was absent and skin biopsy revealed a non-length-dependent small-fiber neuropathy with sympathetic cholinergic and adrenergic post-ganglionic damage in both patients. Nerve conduction studies and evaluation of autonomic control of the cardiovascular system were normal in both patients. Both patients were treated with steroids with good, but partial, (patient 2) recovery of the autonomic dysfunctions.

Although the pathophysiological mechanisms involved are not fully defined, GAD-abs positivity in serum and CSF should be searched in patients with autonomic neuropathy when no other acquired causes are evident. This positivity may help to clarify autoimmune etiology and, subsequently, to consider immunomodulatory treatment.