Differential Diagnosis for a 12-year-old Boy with Fatigue and Dizziness

Single Most Likely Diagnosis

• Anemia: This is a common condition in children and adolescents, especially if they have a poor diet or other underlying conditions. Fatigue and dizziness are classic symptoms of anemia due to the lack of red blood cells or hemoglobin to carry oxygen to tissues.

Other Likely Diagnoses

• Dehydration: Often seen in children who do not drink enough fluids, especially during hot weather or with gastrointestinal illnesses. Dehydration can lead to feelings of fatigue and dizziness.
• Viral Infections: Many viral infections can cause fatigue and dizziness, such as mononucleosis or flu. These are common in children and can present with a variety of symptoms.
• Asthma or Other Respiratory Conditions: Conditions that affect breathing can lead to fatigue and dizziness due to inadequate oxygenation of the blood.
• Diabetes: Though less common, new-onset diabetes (type 1 or 2) can present with fatigue among other symptoms like increased thirst and urination.

Do Not Miss Diagnoses

• Cardiac Conditions (e.g., Hypertrophic Cardiomyopathy): Though rare, cardiac abnormalities can cause dizziness and fatigue due to inadequate cardiac output. Missing these diagnoses can be fatal.
• Neurological Conditions (e.g., Seizure Disorders, Migraines): Certain neurological conditions can present with dizziness and fatigue. Early diagnosis is crucial for appropriate management.
• Hypothyroidism: Though not as common, hypothyroidism can cause fatigue, among other symptoms. It's essential to consider this in the differential due to its impact on quality of life and the availability of effective treatment.
• Sleep Apnea: Can cause significant daytime fatigue and dizziness due to poor sleep quality.

Rare Diagnoses

• Addison's Disease: A rare endocrine disorder that can cause fatigue, dizziness, and other symptoms due to adrenal insufficiency.
• Pernicious Anemia: A rare cause of anemia due to vitamin B12 deficiency, which can lead to fatigue and dizziness.
• Mitochondrial Disorders: Rare genetic disorders affecting the mitochondria, which can cause a variety of symptoms including fatigue and dizziness due to impaired energy production.
• Wilson's Disease: A rare genetic disorder that leads to copper accumulation in the body, potentially causing fatigue among other neurological and hepatic symptoms.

Each of these diagnoses has a different level of likelihood based on the presenting symptoms alone, but considering them in a structured approach helps ensure that potentially serious conditions are not overlooked.