Differential Diagnosis for a Young Woman with Positive Serum ACE, Positive ANA, AC 21 Pattern, and Positive AMA

• Single Most Likely Diagnosis
  • Systemic Lupus Erythematosus (SLE): The presence of a positive ANA is highly suggestive of SLE, especially in a young woman. The AC 21 pattern, although not specific, can be seen in various autoimmune diseases, including SLE. Positive serum ACE can also be found in SLE due to its association with autoimmune phenomena.
• Other Likely Diagnoses
  • Primary Biliary Cholangitis (PBC): Positive AMA is highly suggestive of PBC, an autoimmune disease of the liver. While it primarily affects middle-aged women, it can occur in younger women as well.
  • Sjögren's Syndrome: This autoimmune disorder can present with positive ANA and sometimes positive AMA. It often coexists with other autoimmune diseases like SLE.
  • Mixed Connective Tissue Disease (MCTD): MCTD can present with a combination of features seen in SLE, scleroderma, and polymyositis/dermatomyositis, along with positive ANA and sometimes other autoantibodies.
• Do Not Miss Diagnoses
  • Scleroderma (Systemic Sclerosis): Although less likely, scleroderma can present with positive ANA and sometimes AMA. It's crucial not to miss this diagnosis due to its potential for severe organ involvement.
  • Autoimmune Hepatitis: Positive ANA and AMA can also be seen in autoimmune hepatitis, which requires prompt treatment to prevent liver damage.
• Rare Diagnoses
  • Overlap Syndrome: This refers to conditions where features of two or more different autoimmune diseases coexist (e.g., SLE and PBC). It's rare but important to consider in complex presentations.
  • Juvenile Dermatomyositis: Although primarily a disease of muscle inflammation, it can present with positive ANA and sometimes other autoantibodies, making it a rare consideration in a young woman with these laboratory findings.