What is the diagnosis for a 39-year-old female with a body mass index (BMI) of 17, presenting with muscle weakness, fatigue, shakiness, iron deficiency anemia (serum iron 133, total iron-binding capacity (TIBC) 298, transferrin 225, saturation 44.6%, ferritin 31.9), normal complete blood count (CBC), and normal thyroid-stimulating hormone (TSH) level of 0.81, with a vitamin B12 level of 593?

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Last updated: May 20, 2025 • View editorial policy

Differential Diagnosis for a 39-year-old Female with Muscle Weakness and Fatigue

Single Most Likely Diagnosis

  • Iron Deficiency Anemia: Despite the patient's iron level being within the normal range, the ferritin level is low (31.9), indicating depleted iron stores. The patient's symptoms of muscle weakness, fatigue, and shakiness, along with a low BMI, support this diagnosis. The transferrin level is elevated, and the TIBC is high, which is consistent with iron deficiency anemia.

Other Likely Diagnoses

  • Hypothyroidism: Although the TSH level is within the normal range, some patients may experience symptoms of hypothyroidism even with normal lab values. The patient's symptoms of muscle weakness and fatigue could be related to hypothyroidism, especially if she has a history of thyroid disease or other risk factors.
  • Vitamin Deficiency (other than B12): The patient's normal B12 level does not rule out other vitamin deficiencies, such as vitamin D deficiency, which could contribute to muscle weakness and fatigue.
  • Chronic Fatigue Syndrome: This diagnosis should be considered if other causes of fatigue are ruled out, and the patient's symptoms persist.

Do Not Miss Diagnoses

  • Addison's Disease: Although rare, Addison's disease can cause muscle weakness, fatigue, and weight loss. It is essential to consider this diagnosis, as it can be life-threatening if left untreated.
  • Multiple Myeloma: This condition can cause anemia, fatigue, and muscle weakness. Although the patient's CBC is normal, multiple myeloma can be present even with normal blood cell counts.
  • Hypopituitarism: This rare condition can cause fatigue, muscle weakness, and weight loss. It is essential to consider hypopituitarism, as it can have significant consequences if left untreated.

Rare Diagnoses

  • Mitochondrial Myopathies: These rare genetic disorders can cause muscle weakness, fatigue, and other systemic symptoms.
  • Wilson's Disease: This rare genetic disorder can cause muscle weakness, fatigue, and other systemic symptoms, including liver disease and psychiatric symptoms.
  • Pernicious Anemia: Although the patient's B12 level is normal, pernicious anemia can cause fatigue, muscle weakness, and other symptoms, even with normal lab values.

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.