Vitamin A deficiency. Bitot spots
Causes. The major underlying causes of VAD may be summarized as follows.8,9
Reduced intake
Inadequate food supply
Alcoholism
Mental illness
Dysphagia
Impaired absorption
Crohnβs disease
Celiac sprue
Pancreatic insufficiency
Short bowel syndrome
Chronic diarrhea
Disordered transport
Abetalipoproteinemia
Reduced storage
Liver disease
Cystic fibrosis
Role of zinc. Zinc deficiency may also be involved with the pathogenesis of secondary VAD. Inadequate zinc can depress the hepatic synthesis of retinol-binding protein (RBP), which is required for mobilization of retinol from the liver. In addition, zinc may play a role in the conversion of beta-carotene to retinol via the enzyme 15-15 dioxygenase.10
Causes. The major underlying causes of VAD may be summarized as follows.8,9
Reduced intake
Inadequate food supply
Alcoholism
Mental illness
Dysphagia
Impaired absorption
Crohnβs disease
Celiac sprue
Pancreatic insufficiency
Short bowel syndrome
Chronic diarrhea
Disordered transport
Abetalipoproteinemia
Reduced storage
Liver disease
Cystic fibrosis
Role of zinc. Zinc deficiency may also be involved with the pathogenesis of secondary VAD. Inadequate zinc can depress the hepatic synthesis of retinol-binding protein (RBP), which is required for mobilization of retinol from the liver. In addition, zinc may play a role in the conversion of beta-carotene to retinol via the enzyme 15-15 dioxygenase.10