Differential Diagnosis
- Single most likely diagnosis
- Major depressive disorder (D): The patient's symptoms of insomnia, fatigue, poor appetite, weight loss, and depressed mood are all consistent with a diagnosis of major depressive disorder. The patient's rumination about cancer and death also suggests a depressive disorder.
- Other Likely diagnoses
- Generalized anxiety disorder (C): The patient's rumination about cancer and death could also be indicative of excessive worry, which is a hallmark of generalized anxiety disorder. However, the patient's depressive symptoms are more prominent.
- Somatic symptom disorder (E): The patient's concern about having cancer could be a somatic symptom, but the lack of other somatic symptoms and the presence of depressive symptoms make this diagnosis less likely.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Chronic fatigue syndrome (A): Although the patient's fatigue is more likely due to depression, chronic fatigue syndrome is a possibility that should be considered, especially if the patient's symptoms do not respond to treatment for depression.
- Fibromyalgia (B): Fibromyalgia can cause fatigue, sleep disturbances, and weight loss, but it is typically associated with widespread musculoskeletal pain, which is not mentioned in the patient's symptoms.
- Sleep apnea or other sleep disorders: The patient's insomnia and fatigue could be related to a sleep disorder, which would need to be ruled out with further evaluation.
- Thyroid disorders or other endocrine disorders: The patient's weight loss, fatigue, and sleep disturbances could be indicative of a thyroid disorder or other endocrine disorder, which would need to be ruled out with laboratory tests.
- Rare diagnoses
- Hypothalamic-pituitary-adrenal axis disorders: Disorders such as Cushing's syndrome or Addison's disease can cause weight loss, fatigue, and sleep disturbances, but these are rare and would require specific laboratory tests to diagnose.
- Neurodegenerative disorders: Rare disorders such as frontotemporal dementia or Huntington's disease can cause depression, anxiety, and sleep disturbances, but these are unlikely given the patient's age and lack of other symptoms.