AUTOANTIBODIES
High titer of this antibody correlates with lupus nephritis activity
What is anti-dsDNA?
Acute monoarthritis, negatively birefringent crystals, but normal serum uric acid
What is acute gout (uric acid may be normal during flare)?
Palpable purpura + abdominal pain + IgA deposition
What is IgA vasculitis?
Dry eyes + arthritis + positive anti-SSA in RA patient
What is secondary Sjögren syndrome?
Earliest imaging finding in RA before erosions
What is soft tissue swelling / osteopenia?
This antibody is highly specific for systemic sclerosis but predicts diffuse disease with ILD, not CREST
What is anti-Scl-70 (topoisomerase I)?
CPPD associated with this endocrine disorder frequently tested on boards
What is hyperparathyroidism?
Sinusitis, hematuria, lung nodules, c-ANCA positive
What is granulomatosis with polyangiitis (GPA)?
Photosensitive rash + anti-histone antibodies
What is drug-induced lupus?
MRI finding in inflammatory myopathy
→ What is muscle edema?
Patient with myositis, ILD, Raynaud, and “mechanic’s hands”
What is antisynthetase syndrome (anti-Jo-1)?
Synovial fluid: WBC 40,000 with neutrophil predominance + crystals present
What is septic arthritis must still be ruled out?
Asthma, eosinophilia, neuropathy, p-ANCA
What is eosinophilic GPA (EGPA)?
Proximal muscle weakness but normal CK
What is steroid myopathy?
Gold standard for diagnosing vasculitis type
What is tissue biopsy?
Positive ANA, anti-RNP, overlapping SLE/scleroderma/polymyositis features
What is mixed connective tissue disease (MCTD)?
Recurrent “gout” with normal uric acid and chondrocalcinosis
What is pseudogout (CPPD)?
Young woman, pulseless upper extremities, BP discrepancy
What is Takayasu arteritis?
Raynaud + esophageal dysmotility + calcinosis + telangiectasia
What is CREST (limited systemic sclerosis)?
Definitive test for Sjögren if antibodies negative
What is minor salivary gland biopsy?
This antibody causes false-positive VDRL and paradoxical thrombosis
What is antiphospholipid antibody (lupus anticoagulant)?
Acute gout flare in CKD patient — safest initial therapy
What is corticosteroids?
Renal + pulmonary hemorrhage, negative ANCA, anti-GBM antibodies
What is Goodpasture syndrome?
Inflammatory myopathy with highest malignancy association
What is dermatomyositis?
Joint aspiration finding that distinguishes septic vs inflammatory arthritis
What is Gram stain/culture?