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 (). When aged 1.8 months, her TBA level was found to be as high as 172.0 µmol/L besides the cholestatic alterations (), 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 ().\nAs 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 µmol/L (0–10 µmol/L), and her mother was physically and biochemically healthy (). There was no family history of any genetic diseases.\nPhysical 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.\nBiochemical test at referral revealed a TBA level 50.9 µmol/L with otherwise normal indices (). 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 (); moreover, the patient and her father were both homozygous for the SLC10A1 variant c.800C > T (p.Ser267Phe), while her mother was a carrier (). 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 µmol/L at the age of 3 years and 4 months (), 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.\nThe molecular findings above were further confirmed by Sanger sequencing () and illustrated as family tree diagrams (). The clinical and molecular features of all the 3 patients were summarized in .
Patient 1 was a 5–year-and-11-month-old female referred to the First Affiliated Hospital, Jinan University due to abnormal liver function discovered for 5 years and 7 months. When aged 4 months, she was admitted to a hospital in Guangzhou due to jaundice for 3 months, where physical examination revealed an enlarged liver 4.0 cm below the right costal margin, and a liver function test revealed elevated serum levels of total bilirubin (TBIL), direct bilirubin (DBIL), indirect bilirubin (IBIL), alanine transaminase (ALT), aspartate transaminase (AST), γ-glutamyl transpeptidase (GGT), and alkaline phosphatase (ALP), indicating cholestatic jaundice (). Blood amino acid spectrum analysis by tandem mass spectrometry (MS-MS) revealed raised citrulline, methionine, arginine, and threonine, while large quantities of galactose, galactitol, galactonate, and 4-hydroxyphenyllactate (4HPL) were detected on urinary gas chromatography-mass spectrometry (GC-MS) analysis. Considering the above clinical and laboratory findings, NICCD was suspected, and breast-feeding was stopped while a lactose-free and medium-chain triglycerides (MCT)-enriched formula was introduced. When aged 4.9 months, SLC25A13 genetic analysis in our hospital unveiled a homozygote of the c.852_855del4 mutation () and the diagnosis of NICCD was hence made. Thereafter, besides feeding with the therapeutic formula, supplemental foods rich in protein were encouraged. As a result, her liver function indices got improved gradually and returned to normal by age 10.2 months. However, the hypercholanemia was refractory, with total bile acid (TBA) levels fluctuating from 27.6 µmol/L to 340.2 µmol/L (reference range: 0–10 µmol/L) (). After the age 2 years, the patient showed a fondness for foods rich in protein and fat while an aversion to carbohydrate-rich diets.\nAs the first product of a non-consanguineous couple, the child was delivered spontaneously at the gestational age of 38 weeks and 3 days after an uneventful pregnancy, with a birth weight of 3.0 kg and body length 50 cm. The parents were healthy, and there was no family history of any genetic or infectious diseases.\nPhysical examination revealed a body temperature (T) 36.5°C, heart rate (HR) 115 beats/min (bpm), respiratory rate (RR) 20 bpm, weight (WT) 18 kg, height 107.0 cm. No jaundice was observed in the skin and sclera. The lungs were clear. No murmurs or abnormal heart sounds were heard. There was no abdominal distention, and the liver and spleen were not enlarged. Physiological reflexes were normal and no pathological reflexes could be found on nervous system examination. The extremities were warm, and the distal perfusion was excellent.\nLaboratory investigation showed otherwise normal biochemical indices but a TBA level of 48.7 µmol/L. In view of the intractable hypercholanemia, NTCP deficiency was highly suspected, and SLC10A1 genetic analysis was performed. As a result, the patient was a homozygote, while the parents, carriers, of the reportedly pathogenic variant c.800C > T(p.Ser267Phe)(). NTCP deficiency was thus definitely diagnosed. No specific therapy was given but close clinic follow-up was underway.