ENPP2 and atopic eczema: Furthermore, a decrease in melatonin levels in the GI tract was previously found in patients with PBC which is why a reduction in GI melatonin levels is thought to aggravate the liver disease (19), There are some similarities in the pattern and mechanism of pruritus induced by atopic dermatitis and liver diseases, such as overexpression of the autotaxin enzyme and elevated serum LPA levels.