Question 1 · Hard
A 24-year-old woman with SLE, diagnosed 2 years ago and treated with hydroxychloroquine only, is admitted with new hallucinations and paranoid thoughts. She is afebrile and takes no recreational drugs. CSF cell count, glucose and protein are normal, CSF cultures are negative, and brain MRI is normal. Results: HEp-2 IFA ANA 1:1280, with homogeneous nuclear staining plus dense, fine speckled staining across the cytoplasm; anti-dsDNA 240 IU/mL (positive > 30); C3 58 mg/dL [0.58 g/L] (reference 90-180 mg/dL [0.9-1.8 g/L]); CK and ALP within reference intervals. The additional antibody most likely to be found is:
- AAnti-ribosomal P
- BAntihistone
- CAntimitochondrial (M2)
- DAnti-Jo-1
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Answer: A · Anti-ribosomal P
Anti-ribosomal P antibodies are highly specific for SLE and give a dense fine speckled cytoplasmic pattern on HEp-2 cells, sometimes with nucleolar staining. They are found more often in lupus with neuropsychiatric features, especially psychosis, and also in lupus hepatitis and nephritis. Infection, drugs and structural brain disease have been looked for and not found, which supports neuropsychiatric lupus. Anti-Jo-1 also stains the cytoplasm but goes with myositis and interstitial lung disease, and antimitochondrial antibodies go with primary biliary cholangitis; the normal CK and ALP argue against both. Antihistone antibodies give homogeneous nuclear, not cytoplasmic, staining.
- B: Antihistone antibodies stain nuclei homogeneously and suggest drug-induced lupus; they do not stain cytoplasm.
- C: Antimitochondrial antibodies mark primary biliary cholangitis, and her ALP is normal.
- D: Anti-Jo-1 gives cytoplasmic staining but goes with myositis, and her CK is normal.