Differential Diagnosis for High Ferritin, Iron Saturation, and Weight Loss in a 13-year-old Girl

Single Most Likely Diagnosis

• Anorexia Nervosa: This condition is characterized by low appetite, significant weight loss, and can lead to elevated ferritin levels due to decreased iron utilization and possible inflammation. The psychological aspect of anorexia nervosa, combined with the physical symptoms presented, makes it a strong candidate for the single most likely diagnosis.

Other Likely Diagnoses

• Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease or ulcerative colitis can cause weight loss, decreased appetite, and elevated ferritin due to chronic inflammation. Iron saturation might be affected by the disease's impact on nutrient absorption.
• Chronic Infections: Prolonged infections can lead to elevated ferritin as an acute-phase reactant. Weight loss and decreased appetite are common in chronic infections due to the body's increased metabolic demand and possible gastrointestinal symptoms.
• Autoimmune Disorders: Certain autoimmune diseases, such as juvenile idiopathic arthritis, can present with elevated ferritin due to inflammation, along with systemic symptoms like weight loss and decreased appetite.

Do Not Miss Diagnoses

• Hemophagocytic Lymphohistiocytosis (HLH): A rare but life-threatening condition characterized by excessive immune activation, leading to elevated ferritin levels (often significantly higher than 500 ng/mL), weight loss, and other systemic symptoms. Early diagnosis is crucial for survival.
• Malignancies: Certain cancers, such as lymphomas or leukemia, can cause elevated ferritin, weight loss, and decreased appetite. Although less common in this age group, malignancies are critical to rule out due to their severity.
• Sepsis or Systemic Infections: Severe infections can lead to elevated ferritin, weight loss, and loss of appetite. Identifying and treating the underlying infection promptly is vital.

Rare Diagnoses

• Hyperferritinemia Cataract Syndrome: A rare genetic disorder leading to elevated ferritin levels without iron overload, which could potentially be considered if other causes are ruled out.
• Porphyrias: Certain types of porphyria can cause elevated ferritin and various systemic symptoms, including weight loss and decreased appetite, though they are relatively rare.
• Gaucher's Disease: A genetic disorder that can lead to elevated ferritin among other symptoms, though it's less likely given the specific presentation of weight loss and low appetite without other characteristic symptoms like hepatosplenomegaly.