Congenital lactase deficiency

This code represents a rare, inherited metabolic disorder characterized by the complete absence or severe deficiency of the lactase enzyme from birth. Infants with this condition are unable to digest lactose, the primary sugar in milk, leading to severe gastrointestinal symptoms upon milk ingestion. It is distinct from acquired or adult-onset lactase deficiency.

Use this code for patients, typically infants, diagnosed with primary alactasia or congenital lactase nonpersistence. Documentation should clearly state a diagnosis of congenital lactase deficiency, often supported by genetic testing, hydrogen breath tests, or biopsy results confirming absent lactase activity. This code is appropriate when the condition is present from birth.

• Do not confuse with acquired lactase deficiency (E73.1) or secondary lactase deficiency (E73.8).
• Ensure documentation specifies "congenital" or "primary" to differentiate from other forms of lactase deficiency.
• Consider sequencing this code as the primary diagnosis when it is the reason for the encounter, especially for dietary management or genetic counseling.