Patient 3 was a 1-year-and-2-month-old female referred to our hospital because of abnormal liver function discovered for 12.7 months. At the age 1.3 months, she went through a liver function test because of prolonged jaundice for 1 month, which showed raised levels of AST, GGT, ALP, TBIL, DBIL, and IBIL ( Table 3 ). When aged 1.8 months, her TBA level was found to be as high as 172.0 micromol/L besides the cholestatic alterations ( Table 3 ), and the MS-MS analysis revealed increased levels of tyrosine, citrulline, and methionine while large quantities of urinary 4HPPV and 4HPL were detected on GC-MS analysis. NICCD was consequently suspected, and breast-feeding was stopped while a lactose-free and MCT-enriched formula was suggested. Following that, her cholestatic jaundice got alleviated rapidly and the laboratory alterations recovered to normal levels by the age 5 months, while the hypercholanemia was intractable, even beyond 1 year of age ( Table 3 ).
As the first child of a non-consanguineous couple, the infant was delivered by cesarean section at the gestation age of 38 weeks and 2 days with the birth weight 2,750 g. Her father was clinically healthy with an elevated serum TBA level of 21.1 micromol/L (0-10 micromol/L), and her mother was physically and biochemically healthy ( Table 3 ). There was no family history of any genetic diseases.
Physical examination at referral revealed a body weight 10.1 kg, length 80 cm and head circumference 46 cm. No jaundice was observed in the skin and sclera. Examinations of the heart, the lungs, the abdomen, and nervous system were all normal.
Biochemical test at referral revealed a TBA level 50.9 micromol/L with otherwise normal indices ( Table 3 ). On genetic analysis, the patient was a compound heterozygote of the SLC25A13 mutations c.852_855del4 and c.1638_1660dup, which was inherited from the father and mother, respectively ( Figures 1C, D ); moreover, the patient and her father were both homozygous for the SLC10A1 variant c.800C > T (p.Ser267Phe), while her mother was a carrier ( Figure 1G ). Hence, citrin deficiency and NTCP deficiency were definitely diagnosed for the infant. No specific therapy was given, and his TBA level tended downward to 25.6 micromol/L at the age of 3 years and 4 months ( Table 3 ), still remaining beyond the upper limit. The patient also had a fondness of protein-rich foods while an aversion to carbohydrate-rich foods from the age 1 year.
The molecular findings above were further confirmed by Sanger sequencing ( Figure 2 ) and illustrated as family tree diagrams ( Figure 3 ). The clinical and molecular features of all the 3 patients were summarized in  Supplementary Table 1 .