Elevated serum alkaline phosphatase · generalized pruritus · Dx?

A 34-year-old woman was referred to the hepatology clinic for evaluation of an increased serum alkaline phosphatase (ALP) level. She was gravida 5 and in her 38th week of gestation. Her obstetric history was significant for 2 uncomplicated spontaneous term vaginal deliveries resulting in live births and 2 spontaneous abortions. The patient reported generalized pruritus for 2 months prior to the visit. She had no comorbidities and denied any other symptoms. She reported no family history of liver disease or complications during pregnancy in relatives. The patient did not smoke or drink, and had come to our hospital for her prenatal care visits. The physical exam revealed normal vital signs, no jaundice, a gravid uterus, and acanthosis nigricans on the neck and axilla with scattered excoriations on the arms, legs, and abdomen. Her serum ALP level was 1093 U/L (normal: 50-136 U/L). Immediately before this pregnancy, her serum ALP had been normal at 95 U/L, but it had since been increasing with a peak value of 1134 U/L by 37 weeks' gestation. Serum transaminase activities and albumin and bilirubin concentrations were normal, as was her prothrombin time. The rest of her lab tests were also normal, including her fasting serum bile acid concentration, which was 9 mcmol/L (normal: 4.5-19.2 mcmol/L).