Abdulgayoom Mohammed, Abdelmahmuod Elabbass, Al-Mashdali Abdulrahman F, Abuazab Yara R, Amer Aliaa, Ganwo Ibrahim, Mohamed Shehab
Department of Haematology, National Center for Cancer Care and Research, Hamad Medical Corporation, Doha, Qatar.
Endocrine Section, Department of Medicine, Hamad Medical Corporation, Doha, Qatar.
SAGE Open Med Case Rep. 2025 Sep 15;13:2050313X251377211. doi: 10.1177/2050313X251377211. eCollection 2025.
Megaloblastic anaemia is mainly caused by vitamin B12 or folate deficiency. However, rare cases present with discordant laboratory findings, particularly falsely elevated vitamin B12 levels due to assay interference from anti-intrinsic factor antibodies, complicating diagnosis and management. We describe a 64-year-old woman with macrocytic anaemia, pancytopaenia, and megaloblastic changes on the blood smear, yet with a markedly elevated serum B12 (>2000 pmol/L). A strongly positive anti-intrinsic factor antibody titre explained the paradoxical result. Empirical parenteral B12 therapy led to rapid haematological recovery, confirming masked B12 deficiency secondary to pernicious anaemia. This case highlights the critical pitfall of anti-intrinsic factor antibody-mediated assay interference in vitamin B12 testing, which can mask true deficiency. Clinicians must maintain a high index of suspicion for masked B12 deficiency in patients with megaloblastic anaemia and incongruent laboratory results, particularly in the presence of anti-intrinsic factor antibodies.
巨幼细胞贫血主要由维生素B12或叶酸缺乏引起。然而，罕见病例会出现不一致的实验室检查结果，特别是由于抗内因子抗体的检测干扰导致维生素B12水平假性升高，使诊断和治疗复杂化。我们描述了一名64岁女性，有大细胞贫血、全血细胞减少，血涂片有巨幼细胞改变，但血清B12显著升高（>2000 pmol/L）。抗内因子抗体滴度强阳性解释了这一矛盾结果。经验性肠外B12治疗导致血液学迅速恢复，证实了恶性贫血继发的隐匿性B12缺乏。该病例突出了抗内因子抗体介导的检测干扰在维生素B12检测中的关键陷阱，它可掩盖真正的缺乏。临床医生必须对巨幼细胞贫血且实验室结果不一致的患者，尤其是存在抗内因子抗体的患者，保持对隐匿性B12缺乏的高度怀疑。
