Vitamin A deficiency results in the failure of some cells to differentiate normally. In the sinus, the epithelial lining degenerates into squamous metaplasia resulting in a thickening of the mucus that washes the debris from the | Vitamin A deficiency results in the failure of some cells to differentiate normally. In the sinus, the epithelial lining degenerates into squamous metaplasia resulting in a thickening of the mucus that washes the debris from the |