Comparative study on clinical, laboratory and electrodiagnostic findings of peripheral neuropathy in patients with hypocupremia and hypercupremia, and literature review.

Copper deficiency (hypocupremia) or toxicosis (hypercupremia) may cause disorders of central and peripheral nervous systems. Hypocupremia causes myeloneuropathy resembling vitamin B12 deficiency. However, the clinical manifestations, particularly peripheral neuropathy (PN), of hypercupremia have not been adequately evaluated. To compare clinical, laboratory and electrodiagnositc features of PN between patients with hypocupremia and hypercupremia, we retrospectively reviewed the charts of patients with abnormal copper levels. Subjects with zinc abnormalities were excluded. Five hypocupremia (Male/Female = 4/1; age: 54.6 ± 17.1 years; copper = 55.0 ± 8.5 μg/dL [normal = 72-175]; zinc = 74.4 ± 15.5 μg/dL [normal = 60-130]) and 3 hypercupremia (M/F = 1/2; age: 57.0 ± 8.2 years; copper = 215.0 ± 10.8 μg/dL; zinc = 72.3 ± 14.6 μg/dL) were studied. The notable clinical findings included ambulatory difficulty in hypocupremia (2/5); paresthesia in both hypocupremia (3/5) and hypercupremia (2/3) but pain was only seen in (3/3) hypercupremia patients. Tendon reflexes were decreased in hypocupremia (3/5) and hypercupremia (1/3) but hyperreflexias in hypocupremia (2/5) only. Preexisting comorbidity such as diarrhea were observed in (2/3) hypercupremia but not in hypocupremia patients. Laboratory findings showed vitamin D deficiency (16.4 ± 5.6 ng/mL) in (2/2) hypercupremia but normal (40.4 ± 4.7 ng/mL) in (2/2) hypocupremia. Neurophysiologic studies showed evidence of neuropathy in (3/5) hypocupremia only. Different patterns of clinical, neurological examination and electrophysiologic findings between hypocupremia and hypercupremia suggest different underlying pathophysiologies.