Patient 1. A 2-years-old female infant was referred to the First Affiliated Hospital, Jinan University, due to elevated serum total bile acids (TBA) discovered for 21 months. At the age 3 months, she was admitted to Women and Children's Hospital of Quanzhou because of jaundice for 2 months. Laboratory test revealed that the serum levels of TBA, direct bilirubin (DBIL), aspartate transaminase (AST) and alanine transaminase (ALT) were all elevated (Table 1), and she was thus diagnosed to have cholestatic liver disease. After being treated with intravenous reduced glutathione and ademetionine-1,4-butanedisulfonate for 9 days, which were commonly used in cholestatic patients with elevated alanine transaminase levels, her jaundice was alleviated, but the liver function indices remained abnormal (Table 1). Then oral ursodesoxycholic acid was given and she was discharged at the age 3.3 months. During the subsequent follow-up over 20 months, she showed normal anthropometric and neurobehavioral development without abnormal appearance, and her cholestasis resolved completely since the age 7 months. However, persistently raised TBA levels were observed on repeated biochemical analyses (Table 1). So she was referred to our hospital for further investigation and management when aged 2 years.
The patient was the elder sister of two monochorionic diamniotic twins who was delivered by cesarean section at the gestation age of 37 weeks and 2 days with the birth weight 2.25 kg and body length 45.0 cm. Her father is a hepatitis B virus (HBV) carrier who was clinically healthy but with slightly elevated serum TBA level on biochemistry analysis, and her mother was physically and biochemically healthy (Table 1). There was no family history of any genetic disease.
Physical examination revealed a body weight of 12.0 kg, height 83.5 cm and head circumference 46.0 cm. No jaundice was observed in the skin and sclera. No stridor, crackles or crepitus was heard in the two lungs, and the heart sound was normal without any murmurs. There was no abdominal distention, and the liver and spleen were non-palpable. Physiological reflexes were normal and no pathological reflexes could be found on nervous system examination. On biochemical analysis, the TBA level reached 173.8 mumol/L (0-10 mumol/L) as other indices were normal (Table 1).
Patient 2 was the younger sister of patient 1, who also experienced transient cholestatic jaundice in early infancy and was referred to our hospital with the same complaint of persistently elevated serum TBA levels. As the younger one of two monozygotic twins, her birth weight was 2.30 kg and body length, 46.0 cm. On physical examination at referral, the body weight was 13.0 kg, height 85.0 cm, and head circumference 46.0 cm. No jaundiced skin or sclera was observed. Examinations of the lungs, the heart, the abdomen and nervous system were all normal. Her TBA level was 198.3 mumol/L (0-10 mumol/L), with otherwise normal biochemistry indices (Table 1).
Considering their refractory hypercholanemia whist lack of clinical symptoms and signs on physical examination, NTCP deficiency was highly suspected and hence Sanger sequencing of the SLC10A1 gene was carried out for all family members. As a result, the twins were both homozygotes of the variant c.800C>T (p.Ser267Phe), and their parents were both carriers of the same variant (Figure 1A). Electrophoresis of the PCR-RFLP products showed that the twins both harbored two additional bands of 164 bp and 65 bp rising from the aforementioned SLC10A1 variant, which further confirmed the SLC10A1 genotypes of all family members (Figure 1B).
NTCP deficiency was thus definitely diagnosed, and the twins were followed-up in the local hospital, and no specific medication was given. Thus far, the twins were both healthy but the serum TBA levels were still raised (Table 1), and their long-term outcomes needed to be observed.