Martí Ramon, Spinazzola Antonella, Tadesse Saba, Nishino Ichizo, Nishigaki Yutaka, Hirano Michio
Department of Neurology, Columbia University College of Physicians and Surgeons, New York, NY, USA.
Clin Chem. 2004 Jan;50(1):120-4. doi: 10.1373/clinchem.2003.026179. Epub 2003 Nov 18.
Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is caused by mutations in the gene encoding thymidine phosphorylase (TP). The clinical manifestations of MNGIE are recognizable and homogeneous, but in the early stages, the disease is often misdiagnosed. This study assesses the reliability of biochemical assays to diagnose MNGIE.
We studied 180 patients with clinical features suggestive of MNGIE, 14 asymptomatic TP mutation carriers, and 20 controls. TP enzyme activity in the buffy coat was determined by a fixed-time method, and the plasma nucleosides thymidine (dThd) and deoxyuridine (dUrd) were assessed by a gradient-elution reversed phase HPLC method. TP was sequenced through standard procedures in patients who met the clinical criteria for MNGIE.
Twenty-five of the 180 patients fulfilled the clinical criteria for MNGIE and had homozygous or compound heterozygous TP mutations. All had drastically decreased TP activity [mean (SD), 10 (15) nmol thymine formed. h(-1). (mg protein)(-1) vs 634 (217) nmol thymine formed. h(-1). (mg protein)(-1) for the controls]. Relative to the control mean, TP activities were reduced to 35% in mutation carriers and 65% in MNGIE-like patients. All 25 MNGIE patients had detectable plasma dThd [8.6 (3.4) micromol/L] and dUrd [14.2 (4.4) micromol/L]. Controls, carriers, and MNGIE-like patients showed no detectable plasma dThd and dUrd.
We propose a diagnostic algorithm based on the determination of plasma dThd and dUrd, TP activity in buffy coat, or both to make a definitive diagnosis of MNGIE. Increased concentrations of dThd (>3 micromol/L) and dUrd (>5 micromol/L) in plasma or a decrease in buffy coat TP activity to </=8% relative to controls is sufficient to diagnose MNGIE.
线粒体神经胃肠性脑肌病（MNGIE）由胸苷磷酸化酶（TP）编码基因突变引起。MNGIE的临床表现具有可识别性且较为一致，但在疾病早期常被误诊。本研究评估了生化检测诊断MNGIE的可靠性。
我们研究了180例具有提示MNGIE临床特征的患者、14例无症状TP突变携带者和20例对照。采用固定时间法测定血沉棕黄层中的TP酶活性，采用梯度洗脱反相高效液相色谱法评估血浆核苷胸苷（dThd）和脱氧尿苷（dUrd）。对符合MNGIE临床标准的患者通过标准程序进行TP测序。
180例患者中有25例符合MNGIE临床标准，且有纯合或复合杂合TP突变。所有患者的TP活性均大幅降低[均值（标准差），形成胸腺嘧啶10（15）nmol·h⁻¹·（mg蛋白）⁻¹，而对照组为形成胸腺嘧啶634（217）nmol·h⁻¹·（mg蛋白）⁻¹]。相对于对照均值而言，TP活性在突变携带者中降至35%，在类MNGIE患者中降至65%。所有25例MNGIE患者血浆中均可检测到dThd[8.6（3.4）μmol/L]和dUrd[14.2（4.4）μmol/L]。对照组、携带者和类MNGIE患者血浆中未检测到dThd和dUrd。
我们提出一种基于测定血浆dThd和dUrd、血沉棕黄层中TP活性或两者来明确诊断MNGIE的诊断算法。血浆中dThd（>3μmol/L）和dUrd（>5μmol/L）浓度升高或血沉棕黄层中TP活性相对于对照组降低至≤8%足以诊断MNGIE。
