# Vitamin B12 Deficiency Presenting as Pseudothrombotic Microangiopathy and Intestinal Pseudo-Obstruction

## TL;DR

A case of vitamin B12 deficiency mimicking a rare blood disorder is described, highlighting the importance of early diagnosis to avoid unnecessary treatments.

## Contribution

The paper presents a rare case linking vitamin B12 deficiency to pseudothrombotic microangiopathy and intestinal pseudo-obstruction.

## Key findings

- Vitamin B12 deficiency can mimic thrombotic microangiopathy with hematologic features like macrocytic anemia and thrombocytopenia.
- Treatment with hydroxocobalamin led to full recovery in a patient with pseudo-TMA and gastrointestinal symptoms.
- Pernicious anemia was identified as the underlying cause through autoimmune testing.

## Abstract

Vitamin B12 deficiency is a common and reversible cause of megaloblastic anemia, but in severe cases, it may mimic thrombotic microangiopathy (TMA), a presentation known as pseudothrombotic microangiopathy (pseudo-TMA). This rare entity is frequently underrecognized and may lead to inappropriate therapies if not promptly identified. We report the case of a 62-year-old man who presented with abdominal pain, distension, and constipation, initially raising concern for intestinal obstruction or malignancy. Laboratory evaluation revealed macrocytic anemia, thrombocytopenia, elevated lactate dehydrogenase, and indirect hyperbilirubinemia. Further assessment demonstrated a low reticulocyte count, absence of significant schistocytosis, markedly reduced vitamin B12 levels, and elevated ferritin. Autoimmune testing confirmed pernicious anemia as the underlying etiology. Treatment with intramuscular hydroxocobalamin resulted in complete clinical and hematologic recovery. This case demonstrates the value of recognizing pseudo-TMA and considering vitamin B12 deficiency in patients with TMA-like features and unexplained gastrointestinal symptoms.