This disorder, apparent within 10 days of birth, occurs when brush-border lactase activity (required for the digestion of lactose) in the small intestine is low or absent at birth and is characterized by diarrhea and malabsorption.

• 此病是由于宝宝出生时小肠内的乳糖分解酶素活性很低或没有活性，病症通常在宝宝出生10天内显现：拉肚子以及吸收不良。