What is the diagnosis for an adult with joint pain, synovitis of the arm, pleuritic chest pain, pulmonary embolism (PE), pancytopenia, elevated antinuclear antibody (ANA) titer, hyperferritinemia, and no rash?

Diagnosis: Systemic Lupus Erythematosus (SLE)

The most likely diagnosis is SLE (Option B), given the combination of positive ANA, pancytopenia, pleuritic chest pain with pulmonary involvement, synovitis, and absence of the characteristic features of Adult-Onset Still's Disease.

Key Diagnostic Reasoning

Why SLE is Most Likely

• Positive ANA (1:320) strongly supports SLE, as ANA is present in >95% of SLE patients and is a core serologic criterion 1
• Pancytopenia is characteristic of SLE due to autoimmune destruction of blood cells, occurring in approximately 50% of patients with active disease 1
• Pleuritic chest pain with pulmonary findings fits SLE serositis, which occurs in 30-45% of SLE patients and can present as pleuritis or pericarditis 2
• Synovitis and arthralgia are common in SLE, affecting 90% of patients, typically involving multiple joints 1
• Elevated ferritin (900) is consistent with SLE, as moderate ferritin elevation occurs with inflammation in many autoimmune diseases 1

Why NOT Adult-Onset Still's Disease (AOSD)

The absence of key AOSD features makes this diagnosis unlikely:

• No characteristic salmon-pink evanescent rash, which is present in 85-95% of AOSD cases and typically coincides with fever spikes 1, 3, 4
• Ferritin level of 900 is too low for AOSD, where levels typically range from 4,000-30,000 ng/ml, with extreme levels up to 250,000 ng/ml documented 1
• ANA positivity argues against AOSD, as rheumatoid factor and antinuclear antibodies are characteristically absent in AOSD 1, 3, 4
• No documented high spiking fever ≥39°C, which is a cardinal feature required for AOSD diagnosis, typically occurring daily 1, 4
• Pancytopenia is uncommon in AOSD, which typically presents with marked leukocytosis (>10,000 cells/mm³) with neutrophilia >80% 1, 4

Why NOT Rheumatoid Arthritis (RA)

• RA does not explain the systemic features: pancytopenia, pleuritic chest pain with PE, and the constellation of multi-organ involvement 1
• RA typically presents with symmetric small joint involvement, not the acute systemic presentation described 1
• Positive ANA with systemic features points toward SLE rather than RA 1

Why NOT Infective Endocarditis

• Normal cardiac examination makes endocarditis unlikely, as murmurs are present in 85% of cases 1
• The pattern of autoimmune features (ANA, pancytopenia, synovitis) is not consistent with infection 1
• Pulmonary embolism in endocarditis would typically be septic emboli with different radiographic appearance 1

Clinical Pearls and Pitfalls

Common Diagnostic Pitfalls

• Do not be misled by elevated ferritin alone—the degree of elevation matters. AOSD requires extremely high levels (typically >4,000 ng/ml), while moderate elevation (900 ng/ml) occurs in many inflammatory conditions including SLE 1
• The absence of rash does NOT rule out AOSD, but when combined with other missing features (appropriate ferritin level, leukocytosis, negative ANA), it significantly reduces probability 1
• Pleuritic chest pain can occur in multiple conditions, but when combined with positive ANA and pancytopenia, SLE becomes the unifying diagnosis 2, 5

Key Distinguishing Laboratory Features

AOSD typically shows:

• Marked leukocytosis (>10,000 cells/mm³) with neutrophilia >80% 1, 4
• Extremely elevated ferritin (>4,000 ng/ml, often >10,000 ng/ml) 1
• Negative ANA and RF 1, 3, 4
• Glycosylated ferritin <20% (when available) 1

SLE typically shows:

• Cytopenias (leukopenia, thrombocytopenia, anemia) 1
• Positive ANA (>95% of cases) 1
• Moderate ferritin elevation reflecting inflammation 1
• Often positive anti-dsDNA and low complement levels 1

Next Steps for Confirmation

• Obtain anti-dsDNA antibodies and complement levels (C3, C4) to confirm SLE diagnosis 1
• Check complete autoantibody panel including anti-Smith, anti-Ro, anti-La 1
• Evaluate for other SLE manifestations: renal involvement (urinalysis, creatinine), neurologic involvement 1
• Address the pulmonary embolism with appropriate anticoagulation, as thrombotic events can occur in SLE, particularly with antiphospholipid antibodies 5