Muscle Injury or Trauma: This is often the most common cause of elevated creatine kinase (CK) levels, as CK is an enzyme found in muscle cells. An injury could lead to muscle cell damage, releasing CK into the bloodstream. Elevated hemoglobin could be seen if there's associated internal bleeding or if the child has experienced significant physical stress leading to hemolysis.

Viral Myositis: Certain viral infections can cause inflammation of the muscles (myositis), leading to elevated CK levels. Common culprits include coxsackieviruses and influenza viruses. Hemoglobin levels might be elevated due to dehydration or a stress response.
Sickle Cell Crisis: Although less common in a 3-year-old without a known history, sickle cell disease can cause episodes of acute illness (crises) characterized by pain and potentially elevated CK due to muscle infarction. Hemoglobin levels might be elevated due to dehydration or as a response to chronic anemia.
Inherited Muscle Disorders: Conditions like Duchenne muscular dystrophy or Becker muscular dystrophy can present with elevated CK levels due to ongoing muscle damage. However, these conditions typically have other clinical manifestations and might not directly explain elevated hemoglobin.

Malignant Hyperthermia: A life-threatening medical emergency that can occur in response to certain anesthetics or stressors, leading to extremely high CK levels and potentially elevated hemoglobin due to muscle breakdown and hemolysis. Prompt recognition and treatment are crucial.
Rhabdomyolysis: A serious syndrome due to direct or indirect muscle injury, leading to the death of muscle fibers and release of their contents into the bloodstream. This can cause extremely high CK levels and potentially affect kidney function. Elevated hemoglobin could be seen due to muscle breakdown.
Severe Infections (e.g., Meningococcemia): Certain severe bacterial infections can cause significant stress, leading to elevated CK and potentially affecting hemoglobin levels due to sepsis-induced hemolysis or other mechanisms.

Mitochondrial Myopathies: A group of disorders affecting the mitochondria, which can lead to muscle weakness and elevated CK levels. These conditions are rare and often have other systemic manifestations.
Glycogen Storage Diseases: Certain types of these diseases can lead to muscle damage and elevated CK levels, especially after exercise or fasting. They might also have effects on hemoglobin levels indirectly through chronic disease processes.
McArdle Disease (Glycogen Storage Disease Type V): A rare genetic disorder that affects the muscle cells' ability to break down glycogen, leading to elevated CK levels after exercise. It's less likely to directly cause elevated hemoglobin but could be part of a broader differential for unexplained muscle symptoms.