Department of Internal Medicine, Louisiana State University Health Shreveport, Shreveport, LA, USA.
Department of Internal Medicine, Medical Student, Louisiana State University Health Shreveport, Shreveport, LA, USA.
Fam Pract. 2024 Jun 12;41(3):388-391. doi: 10.1093/fampra/cmad065.
Pseudo-thrombotic microangiopathy (pseudo- thrombotic microangiopathy (TMA)) is a rare presentation of B12 deficiency. Overlapping features like elevated LDH/total bilirubin with low haemoglobin/haptoglobin/platelets could deceivingly suggest thrombotic thrombocytopenic purpura (TTP) resulting in avoidable procedures/treatments.
A 36-year-old female with hypothyroidism initially presented to clinic with fatigue, palpitations, lightheadedness, and dyspnoea over a 3-month duration and was found to have a haemoglobin of 5.7 g/dL. She received two packed red blood cell units in the emergency room and subsequently discharged with outpatient follow-up and empiric oral iron. During her follow-up visit, she was found to have easy bruisability, gum bleeding, and generalized weakness from hemolytic anaemia (mean corpuscular volume (MCV) 90 fL, haptoglobin <8 mg/dL, LDH >4,000 U/L and schistocytosis on CBC) and thrombocytopenia of 52 K/uL. Due to PLASMIC score of 6 and suspicion for TTP, she was transferred to our facility and tr eated with three cycles of plasma exchange and prednisone but were discontinued when ADAMTS13 levels returned normal. While the patient had normal B12 levels, further testing revealed positive intrinsic factor antibodies (IF-Ab) and an elevated MMA level of 1.56 umol/L. Replacement with cobalamin led to normalization of labs and symptoms.
Timely diagnosis of pseudo-TMA was exceptionally challenging due to several overlapping features with TTP including normal B12 and normal MCV. B12 levels may falsely appear normal in pernicious anemia due to IF-Ab interference with chemiluminescent immunoassay. Schistocytes lower the MCV in automated cell counters. Lower reticulocyte index (<2%), presence of immature/large platelets and teardrop cells, elevated MMA and a higher LDH (>2500) are indicative of B12 deficiency.
假性血栓性微血管病（假性血栓性微血管病（TMA））是 B12 缺乏的一种罕见表现。类似升高的 LDH/总胆红素与低血红蛋白/触珠蛋白/血小板等重叠特征可能会误导性地提示血栓性血小板减少性紫癜（TTP），从而导致可避免的程序/治疗。
一名 36 岁女性患有甲状腺功能减退症，最初因疲劳、心悸、头晕和呼吸困难在 3 个月内到诊所就诊，发现血红蛋白为 5.7 g/dL。她在急诊室接受了两次红细胞悬液输注，随后出院接受门诊随访和经验性口服铁剂治疗。在随访就诊时，她因溶血性贫血出现易瘀伤、牙龈出血和全身无力（平均红细胞体积（MCV）90 fL，触珠蛋白<8 mg/dL，LDH>4000 U/L 和血涂片有棘形红细胞）和血小板计数为 52 K/uL。由于 PLASMIC 评分为 6 分且怀疑 TTP，她被转至我们医院并接受了三个周期的血浆置换和泼尼松治疗，但当 ADAMTS13 水平恢复正常时停止了治疗。虽然患者的 B12 水平正常，但进一步的检测显示阳性内因子抗体（IF-Ab）和升高的 MMA 水平为 1.56 umol/L。补充钴胺素导致实验室和症状正常化。
由于与 TTP 有几个重叠特征，包括正常的 B12 和正常的 MCV，假性 TMA 的及时诊断极具挑战性。由于 IF-Ab 干扰化学发光免疫测定，恶性贫血可能导致 B12 水平假性正常。血涂片有棘形红细胞会降低自动细胞计数器的 MCV。较低的网织红细胞指数（<2%）、不成熟/大血小板和泪滴细胞、升高的 MMA 和更高的 LDH（>2500）提示 B12 缺乏。
