Differential Diagnosis for Darkening of Hands and Feet with Hemoglobin Level 11.4 on Methotrexate
- Single Most Likely Diagnosis
- Methotrexate-induced skin hyperpigmentation: This condition is a known side effect of methotrexate, a medication used in the treatment of various cancers and autoimmune diseases. The darkening of skin, particularly on the hands and feet, can occur due to the deposition of melanin or other pigments as a result of the drug's effect on skin cells.
- Other Likely Diagnoses
- Anemia of chronic disease: Although the hemoglobin level is 11.4, which is near the lower limit of normal, anemia of chronic disease could contribute to skin changes, including pallor or, less commonly, hyperpigmentation, especially if there's an underlying inflammatory or malignant process.
- Vitamin B12 deficiency: Methotrexate can interfere with folate metabolism, and while it's less direct, a deficiency in vitamin B12 (which is closely related to folate in hematopoiesis) could potentially contribute to skin changes, including hyperpigmentation, in addition to affecting hemoglobin levels.
- Do Not Miss Diagnoses
- Sickle cell disease or other hemoglobinopathies: Although the hemoglobin level is provided, these conditions can cause skin hyperpigmentation due to chronic hemolysis and could be exacerbated by certain medications. Missing these diagnoses could lead to significant morbidity and mortality if not properly managed.
- Porphyria cutanea tarda: This is a disorder that can cause blistering and skin fragility on sun-exposed areas, leading to scarring and hyperpigmentation. It's associated with liver disease, iron overload, and certain medications, including possibly methotrexate.
- Rare Diagnoses
- Addison's disease: This condition, characterized by adrenal insufficiency, can cause hyperpigmentation, particularly in areas exposed to the sun, as well as in palmar creases, scars, and other areas. However, it would typically be associated with other systemic symptoms such as fatigue, weight loss, and hypotension.
- Arsenic poisoning: Chronic exposure to arsenic can lead to skin hyperpigmentation, among other symptoms. Although rare, it's an important consideration in certain environmental or occupational contexts.
- Erythromelalgia: A disorder characterized by burning pain, heat, and redness in the hands and feet, which could potentially be confused with or contribute to the perception of darkening due to increased blood flow and inflammation.