Abstract
Vitamin B12 (cobalamin) deficiency is a commonly seen nutritional deficiency that presents with a broad spectrum of clinical symptoms. In this report, we describe a case of a 49-year-old female patient who presented to the emergency department with sudden onset of a syncopal-like episode, generalized weakness, and severe pancytopenia, who was subsequently diagnosed with vitamin B12 deficiency upon admission. The patient underwent a thorough evaluation to exclude alternative etiologies for her presentation. Her clinical symptoms and blood count significantly improved after six days of treatment with vitamin B12 supplementation. While vitamin B12 deficiency is a commonly recognized issue, healthcare providers should be aware of its infrequent presentations. Our case serves as a reminder to clinicians to remain vigilant for acute onset manifestations and consider vitamin B12 deficiency as a differential diagnosis for the early management of pancytopenia.