Lactase deficiency may be present at birth, may develop immediately after weaning, or may not become evident until puberty or later.
Congenital lactase deficiency is sometimes permanent but is more often temporary. It is caused by delayed enzyme maturation, and occurs especially in premature babies. Permanent lactase deficiency develops in about 80 to 90 percent of blacks and Orientals and in about 15 percent of whites. Lactase deficiency may also occur as a complication of intestinal diseases (including celiac disease and gastroenteritis); in such cases, the deficiency often disappears as the disease improves.
Symptoms, diagnosis, and treatment of lactase deficiency
Undigested lactose ferments in the intestine and causes severe abdominal cramps, bloating, flatulence, and diarrhea; weight loss and malnutrition may also occur.
The diagnosis can be confirmed by tests on blood and feces. Treatment is a lactose-free diet; milk must be avoided but fermented milk products, such as yogurt, can be eaten. Enzyme replacements (which break down lactose either partially or fully) may be used in some cases.