Congenital lactase deficiency


Type of disease: Rare conditions

Congenital lactase deficiency (CLD) is a disorder where infants do not produce the enzyme lactase. Lactase helps digest lactose (milk sugar) in dairy products, including formula and breast milk.

Infants with CLD often become severely dehydrated, lose weight, and are malnourished. Diarrhea may occur after feeding with certain formula and breast milk as well. The stomach of the infant might also appear swollen and larger than normal. These symptoms begin a short period, often days, after birth. Reaction to lactose in the diet is more severe in those with CLD because there is no lactase in the body, whereas older individuals with lactose intolerance have trace amounts of lactase to help digest some lactose.

CLD is caused by changes in the LCT gene. Genes are made up of two alleles, one from the mother and one from the father. CLD is inherited in an autosomal recessive manner meaning that an individual must have two copies of the mutation that causes the condition. A person with one mutated gene is a carrier of the disorder but usually will not have any symptoms. A person has the disorder if they receive two copies of the mutated gene.

For diagnosis, physicians often remove lactose from the infant’s diet and monitor whether the symptoms improve. Other common tests include a hydrogen gas breath test, stool sample analysis, and genetic testing. They can also biopsy (sample) part of the small intestine to test for lactase deficiency or measure calcium levels in the blood and kidneys. (High calcium levels have been observed in individuals with congenital lactase deficiency).

There is currently no cure, but keeping the individual of a lactose-free diet will relieve symptoms. If you or a family member has been diagnosed with CLD, talk with your doctor about the most current treatment options. Support groups may also provide resources for support and information.

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