Congenital lactose intolerance
It is an autosomal recessive disorder. In very rare cases, babies show symptoms of lactose intolerance with the onset of nursing. On biopsies they have normal small intestinal cell structure, but have undetectable lactase activity. The underlying cause for this is their genetic makeup. In these rare unfortunate cases, they have of a pair of recessive alleles that are mutated versions of normal alleles of the lactase-phlorizin hydrolase (LPH) gene. They may be in the form of stop codons in the coding region of the gene. These faulty alleles express in the form of misfolded protein that lacks proper enzymatic activity of lactase and are degraded afterwards. [3]