Vitamin B12 deficiency, extrathoracic airway mucosa and dysfunction.

Background: We previously found a strong association between extrathoracic airway dysfunction(EAD) and nutritional deficiency(vitaminB12,iron). We investigated if damage of theupper airway mucosa underlines this association. Methods: We performed pharyngeal biopsy in 10 nonsmoking patients with symptoms consistent with EAD (cough, dysphonia, chocking, pharyngodynia) and vitamin B12 deficiency(below 300 pg/ml). The patients were 5 men and 5 women, aged 45years(SD18);all had normal lung function tests and a negative history for asthma. Five asymptomatic subjects, matched for age, without nutritional deficiency served as controls. Both patients and controls underwent histamine inhalation challenge with assessment of bronchial (PC20FEV1) and EA(PC25MIF50)threshold. Results: All the patients had EA dysfunction, only 2 of them had mild bronchial hyperresponsiveness. Mean PC25MIF50 was 2.55mg/ml(SD2.24), meanPC20FEV1 was 25.3mg/ml (SD12.5). Histamine challenge was negative in all control subjects. Morphometric analysis of pharyngeal mucosa showed that patients, as compared with controls, had a significant epithelium thinning (133.7±55 μm, versus 230.8±9 μm, p=0.002). PC25MIF50 was significantly related to epithelium thickness (r= 0.701, p=0.008). Conclusion: Our findings indicate that vitamin B12 deficiency may favour EA dysfunction by decreasing mucosal trophism. This observation suggests that nutritional disorders may contribute to respiratory symptoms and airway dysfunction