Differential Diagnosis for Abnormal Weight Loss

Abnormal weight loss can be caused by a variety of factors, ranging from benign to life-threatening conditions. The following differential diagnosis is organized into categories to help guide the diagnostic process.

• Single Most Likely Diagnosis

  • Depression: Often presents with changes in appetite and weight. Given its high prevalence, it is a common cause of abnormal weight loss.
  • Diabetes Mellitus: Uncontrolled diabetes can lead to weight loss due to the body's inability to use glucose for energy, leading to the breakdown of fat for fuel.

• Other Likely Diagnoses

  • Hyperthyroidism: An overactive thyroid gland can increase metabolism, leading to weight loss despite increased appetite.
  • Gastrointestinal Disorders (e.g., celiac disease, Crohn's disease, ulcerative colitis): These conditions can lead to malabsorption of nutrients, resulting in weight loss.
  • Chronic Infections (e.g., tuberculosis, HIV): Chronic infections can cause weight loss due to increased metabolic demand and decreased appetite.
  • Cancer: Although not the most common cause, certain types of cancer (e.g., pancreatic, lung, stomach) can present with unexplained weight loss.

• Do Not Miss Diagnoses

  • Malignancy: While cancer is not the most common cause of weight loss, missing a diagnosis of cancer can be devastating. All types of cancer should be considered, especially those that are common or have a poor prognosis if diagnosed late.
  • AIDS: Acquired Immunodeficiency Syndrome can cause significant weight loss and is critical to diagnose early for appropriate management.
  • Pituitary or Adrenal Gland Disorders: Conditions affecting these glands can lead to hormonal imbalances that result in weight loss and are crucial to identify due to their impact on health.

• Rare Diagnoses

  • Addison's Disease: A rare endocrine disorder in which the adrenal glands do not produce enough cortisol and aldosterone, leading to weight loss among other symptoms.
  • Whipple's Disease: A rare, systemic bacterial infection that can cause malabsorption and weight loss.
  • Amyotrophic Lateral Sclerosis (ALS): A progressive neurodegenerative disease that can lead to weight loss due to difficulty swallowing and decreased appetite.

Each of these diagnoses requires careful consideration of the patient's history, physical examination, and laboratory tests to determine the underlying cause of abnormal weight loss.