Objective:

To report a case of systemic lupus erythematosus (SLE) associated with a small paroxysmal nocturnal hemoglobinuria (PNH) clone and to analyze clinical manifestations and outcomes in patients with SLE–PNH overlap.

Approach:

• Case Presentation: A 42-year-old woman with persistent pancytopenia was diagnosed with SLE and identified to have GPI-deficient clones consistent with PNH using high-sensitivity flow cytometry.
• Literature Review: A systematic review of seven additional cases of SLE-associated PNH was conducted to analyze clinical manifestations, PNH clone size, treatment strategies, and outcomes.

Key Findings:

• Thrombotic events occurred in 37.5% (3/8) of patients with SLE-associated PNH.
• Detectable hemolysis was present in 87.5% (7/8) of patients.
• Small PNH clones (<10% granulocytes) may contribute to clinical hemolysis in SLE patients.

Interpretation:

The findings indicate that small PNH clones, traditionally deemed clinically insignificant, may be associated with hemolysis in SLE patients due to autoimmune complement activation.

Limitations:

• The co-occurrence of SLE and PNH is rarely reported, leading to limited understanding of its clinical characteristics.
• The analysis is based on a small number of cases, which may not represent the broader population.

Conclusion:

The study highlights the importance of PNH screening in SLE patients with unexplained cytopenia or Coombs-negative hemolysis, advocating for management based on clinical phenotype rather than clone size.