You should suspect systemic iron toxicity if a patient presents with:

Systemic iron toxicity is a critical condition that can occur after ingestion of a significant amount of iron, often seen in children who consume iron supplements. Among the options provided, hematemesis, which is the vomiting of blood, is a compelling indicator of iron toxicity. This symptom occurs because iron can irritate the gastrointestinal tract, leading to ulceration or bleeding.

Additionally, iron can cause corrosive damage to the mucosal lining of the stomach and intestines, which can result in gastrointestinal hemorrhage, manifesting as hematemesis. When assessing a patient suspected of having systemic iron toxicity, the presence of hematemesis suggests that there is significant irritation or injury to the stomach lining, which is a serious complication that needs immediate medical attention.

In contrast, while symptoms such as severe nausea and bradypnea may occur in various medical conditions, they are not specifically indicative of systemic iron toxicity. Hypertension may arise in response to stress or other factors but is not a hallmark sign of iron toxicity. Therefore, the most relevant and concerning symptom in the context of systemic iron toxicity is hematemesis.