Unexplained chronic cough and vitamin B-12 deficiency.

摘要

BACKGROUND: Chronic cough is characterized by sensory neuropathy. Vitamin B-12 (cobalamin) deficiency (Cbl-D) causes central and peripheral nervous system damage and has been implicated in sensory neuropathy and autonomic nervous system dysfunction. OBJECTIVE: We evaluated whether Cbl-D has a role in chronic, unexplained cough. DESIGN: Laryngeal threshold (histamine concentration that provokes a 25% decrease in the midinspiratory flow), bronchial threshold (histamine concentration that provokes a 20% decrease in the forced expiratory volume in 1 s), and cough threshold (histamine concentration that causes >/=5 coughs) in response to an inhaled histamine were assessed in 42 patients with chronic, unexplained cough [27 Cbl-D patients and 15 patients without Cbl-D (Cbl-N)] before and after intramuscular injections of cobalamin for 2 mo. Laryngeal, bronchial, and cough hyperresponsiveness was diagnosed when histamine concentration thresholds were