Differential Diagnosis

The following list provides a neutral differential diagnosis based on the provided information, without assuming any cause or suggesting treatment.

• Single most likely diagnosis
  • Anorexia Athletica or Female Athlete Triad: The patient's history of high-level rhythmic gymnastics, low weight, decreased appetite, and symptoms such as dizziness, fatigue, and shortness of breath on exertion are consistent with this diagnosis. The combination of disordered eating, amenorrhea, and osteoporosis (suggested by severe vitamin D deficiency) further supports this possibility.
• Other Likely diagnoses
  • Mitochondrial Myopathy: The patient's progressive difficulty with sports, rapid fatigue, shortness of breath on exertion, and muscle hypotrophy on ultrasound are consistent with a mitochondrial myopathy. The EMG findings of mild low amplitude, short duration, and mild polyphasia also support this diagnosis.
  • Cardiac Arrhythmia: The patient's history of tachycardia, syncope, and abnormal Holter findings (focal atrial tachycardia) suggest a cardiac arrhythmia as a contributing factor to her symptoms.
  • Restrictive Lung Disease: The patient's PFTs show a reduced FVC and VC, with an elevated RV/TLC ratio, which may indicate a restrictive lung disease. However, the normal inspiratory HRCT and DLCO make this diagnosis less likely.
• Do Not Miss diagnoses
  • Cardiac Sarcoidosis: Although less likely, cardiac sarcoidosis can cause arrhythmias, heart failure, and sudden death. The patient's abnormal Holter findings and history of syncope make it essential to consider this diagnosis.
  • Pulmonary Embolism: The patient's shortness of breath on exertion and history of syncope could be indicative of a pulmonary embolism, which would be a medical emergency.
  • Hypokalemic Periodic Paralysis: The patient's history of muscle weakness, fatigue, and arrhythmias could be consistent with hypokalemic periodic paralysis, which can be life-threatening if not recognized and treated promptly.
• Rare diagnoses
  • Kearns-Sayre Syndrome: This rare mitochondrial myopathy can cause progressive external ophthalmoplegia, heart block, and respiratory failure. Although less likely, the patient's muscle hypotrophy and abnormal EMG findings make it a consideration.
  • Glycogen Storage Disease: The patient's history of fatigue, shortness of breath on exertion, and muscle hypotrophy could be consistent with a glycogen storage disease, such as McArdle disease. However, the normal echocardiogram and lack of other specific findings make this diagnosis less likely.