Differential Diagnosis for Progressive Weakness in an Elderly Male with Worsening Vitiligo

Single Most Likely Diagnosis

• Autoimmune Polyendocrinopathy Type 2 (APS-2): This condition is characterized by the presence of autoimmune Addison's disease, thyroiditis, and/or type 1 diabetes mellitus, often accompanied by other autoimmune diseases such as vitiligo. The progressive weakness could be due to adrenal insufficiency or other endocrine imbalances.

Other Likely Diagnoses

• Vitamin B12 Deficiency: This can cause progressive weakness, and there's an association between vitamin B12 deficiency and autoimmune diseases, including those that cause vitiligo. The deficiency could be due to pernicious anemia, an autoimmune condition affecting the stomach's ability to absorb vitamin B12.
• Thyroid Disease: Both hypothyroidism and hyperthyroidism can cause progressive weakness. The association between thyroid diseases and vitiligo, as well as other autoimmune conditions, makes this a plausible diagnosis.
• Diabetes Mellitus Type 1: Although less common in the elderly, type 1 diabetes can occur at any age and is associated with other autoimmune conditions, including vitiligo. Progressive weakness could be a symptom of uncontrolled diabetes.

Do Not Miss Diagnoses

• Adrenal Insufficiency (Addison's Disease): This is a life-threatening condition that can cause progressive weakness among other symptoms. Its association with vitiligo and other autoimmune diseases makes it crucial not to miss.
• Multiple Myeloma: Although less likely, multiple myeloma can cause progressive weakness and is associated with various skin manifestations, including potentially vitiligo-like symptoms due to amyloid deposition. Given its severity, it's essential to consider.
• Lymphoma: Certain types of lymphoma can cause progressive weakness and are associated with autoimmune phenomena, including vitiligo. The potential severity of lymphoma necessitates its inclusion in the differential diagnosis.

Rare Diagnoses

• Aleukemic Leukemia Cutis: A rare condition where leukemia cells infiltrate the skin, potentially causing skin manifestations that could mimic or exacerbate vitiligo. Progressive weakness could be due to underlying leukemia.
• POEMS Syndrome: A rare paraneoplastic syndrome associated with a plasma cell disorder, characterized by polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy, and skin changes, which could include vitiligo-like symptoms. Progressive weakness is a common symptom due to the neuropathy.