Jos Jansen

72 Chapter 3 Individuals with mutations in TMEM199 (Table 1) showed a mild clinical presentation with hypercholesterolemia and elevated low-density lipoprotein cholesterol (LDL-C), elevated alkaline phosphatase (ALP, bone-derived) and aminotransferases (ATs, consisting of aspartate aminotransferase [AST] and alanine aminotransferase [ALT]). Liver biopsy showed lipid degeneration and mild steatosis with minimal fibrosis. In addition, slight abnormalities of copper metabolism were noted. However, sequencing of ATP7B (MIM: 606882) for a diagnosis of Wilson disease (WD [MIM: 277900]) failed to detect a mutation. Total cholesterol levels were in between those of control individuals and individuals with familial hypercholesterolemia (FH [MIM: 143890]). Inspection of the raw exome-sequencing data from three individuals revealed no mutations in genes known to be associated with FH ( LDLR [MIM: 606945], APOB [MIM: 107730], PCSK9 [MIM: 607786]), although coverage was very poor for exon 1 of these three genes and for exon 10 of PCSK9 . Total cholesterol levels of the parents were not measured. The birth and early childhood of brothers F1-II2 and F1-II3, born 1990 and 1998, respectively, to Greek consanguineous parents, was unremarkable. During a routine blood test at fourteen and six years of age, respectively, elevated serum ATs and ALP were noticed (F1-II2: ALT 54 U/l [normal range, 0–50 U/l], AST 73 U/l [normal range, 0–50 U/l], ALP 745 U/l [normal range, < 360 U/l]; F1-II3: ALT 210 U/l, AST 246 U/l, ALP 1162 U/l). Gammaglutamyl transferase (gGT) and bilirubin levels were normal. A liver ultrasound was normal and liver biopsy showed steatosis. Their clinical appearance was unremarkable, and their growth and psychomotor development were normal. Isoelectric focusing (IEF) of transferrin (Tf) showed a type 2 CDG profile. Further biochemical analysis showed low serum ceruloplasmin for individual F1-II2 (11.5 mg/dl [normal range, 15–60 mg/dl]) and low-normal ceruloplasmin for individual F1-II3 (15.6 mg/dl). On suspicion of WD, a slightly elevated 24 hr urinary copper/creatinine ratio was found (86.9 and 72.8 mg/g creatinine [normal range, < 60mg/g creatinine]). However, Kayser-Fleischer rings were absent, and genetic testing for ATP7B found no mutations, therefore a diagnosis of WD was discarded. Additionally, both siblings had elevated levels of total cholesterol (F1-II2: 253 mg/dl [normal range, 120–200 mg/dl]; F1-II3: 336 mg/dl) and LDL-C (F1-II2: 188 mg/dl [normal range, 50–130 mg/dl]; F1-II3: 277 mg/dl). Several coagulation factors were slightly decreased (antithrombin- III, factor XI, factor XIII, and protein S), but the international normalized ratio was normal. During subsequent years, ATs, ALP, and total cholesterol fluctuated from normal to approximately 1.5 times the upper level of normal.