A 27-year-old man came to an internal medicine clinic referred by his primary care doctor for: asthenia of three months' duration, non-specific dizziness and intermittent epigastralgia of moderate intensity. Relevant personal history: allergic rhinoconjunctivitis. His usual treatment consisted of ebastine 10 mg once daily during the seasonal allergy period.

Examination revealed marked pallor of the skin and mucous membranes. Blood tests showed haemoglobin 6.5 g/dL (13-18 g/dL), mean corpuscular volume 125 fl (80-100 fl), leucocytes 6,000/mL (4,000-10,500/mL), platelets 280,000/mm3 (150. 000-400,000/mm3, total bilirubin 1.35 mg/dL (0.3-1.2 mg/dL), aspartate aminotransferase (AST) 140 IU/L (4-50 IU/L), alanine aminotransferase (ALT) 410 IU/L (5-47 IU/L), lactate dehydrogenase (LDH) 4,186 IU/L (140-240 IU/L). In view of this analysis, a blood smear was requested which showed anisocytosis with a macrocytic tendency, hypersegmentation of neutrophils and some dacryocytes. Iron and folic acid levels were normal, with serum vitamin B12 levels of 62 pg/mL (180880 pg/mL) and homocysteine of 32 μmol (4-15 μmol/L). Gastrin levels are clearly elevated 539 pg/mL (normal < 100 pg/mL). Treatment was started with intramuscular injections of 1,000 μg/day of vitamin B12 for 7 days, then weekly for one month and maintenance therapy with one injection per month.

The haemogram normalised in the fourth week of treatment.