MUC5B Mutation Causes Mucociliary Dysfunction and Primary Ciliary Dyskinesia Like Illness in a Saudi Girl: A Case Report

Abstract

1.1. Background: MUC5B is a major gel forming mucin in the lung that plays a key role in mucociliary clearance and host defense that is secreted from proximal submucosal glands and distal airway secretory cells. The MUC5B promoter variant is associated with enhanced expression of the MUC5B transcript in lung tissue from unaffected subjects and patients with idiopathic pulmonary fibrosis (IPF). In patients with IPF, excess MUC5B protein is especially observed in epithelial cells in the respiratory bronchiole and honeycomb cysts, regions of lung involved in lung fibrosis. However, it remains unclear how MUC5B leads to the development of IPF in adult. In mice, MUC5B is required for mucociliary clearance and for controlling inflammation after microbial exposure. The consequences of its loss in humans are unclear, however MUC5B homozygous variant has recently been reported in two affected siblings.