Lactase inherited deficiency

The malabsorption of specific substances tends to occur in certain w ell-defined conditions such as vitamin B, malabsorption which leads to pernicious anaemia. This occurs when intrinsic factor production is lost due to gastric mucosal atrophy. Patients may also have inherited deficiencies of intestinal saccharidases such as lactase which cause malabsorption when the patient drinks milk or cats milk products. This is known as lactose intolerance. 

EXAMPLE 11.5 What is the consequence of an acquired or inherited deficiency of lactase ... 

The question has arisen of whether lactase deficiency is inherited or acquired. In most mammals, lactase declines to low levels or is entirely absent after weaning. It would seem entirely feasible that it could be an acquired characteristic in people who customarily do not drink milk. 

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