Rheumatology — 5-min cram sheet — TheStudyFix Medical Library

Written by Betra Youhanna, a medical student and not a doctor — check every detail against your own teaching.

A quick revision sheet. Check current teaching and clinical guidance before using any detail in patient care.

Rheumatology — 5-min cram sheet

_Built from the rheum disease index. Deck-faithful._

Buzzword → answer (the vignette reflex)

Gottron's papules / heliotrope (purplish) eyelid rash → Dermatomyositis (Gottron's pathognomonic for DM; PM has NO rash)
Keratoderma blenorrhagica → Reactive arthritis (pathognomonic)
1st MTP "podagra" → Gout (50–70% of first attacks)
Needle-shaped, strongly negatively birefringent crystals (yellow ∥ to axis) → Gout (MSU)
Rhomboid, weakly positively birefringent crystals (blue ∥ to axis) → Pseudogout (CPPD)
Chondrocalcinosis (linear cartilage calcification) → CPPD (most common cause)
Watermelon stomach / GAVE → limited SSc (CREST)
Pencil-in-cup deformity on X-ray → Psoriatic arthritis
Bamboo spine / dagger sign / Romanus shiny-corner → Ankylosing spondylitis
Halo sign on temporal-artery ultrasound → Giant cell arteritis
Positive pathergy test → Behçet's (also: aortic aneurysm on imaging = Behçet's or Takayasu)
Jaccoud's arthropathy (reducible, non-erosive, correctable) → SLE
Erysipelas-like lesion (lower leg) + recurrent polyserositis → FMF
Asthma + eosinophilia → EGPA (Churg–Strauss); ENT + lung + kidney + cANCA → GPA (Wegener's)

Antibody → disease

Antibody	Disease / association
Anti-CCP	RA — 97% specific, marker of erosive disease
RF (IgM vs IgG Fc)	RA — >80%, high titre tracks severity / extra-articular / nodules
dsDNA, Sm	SLE (anti-Sm highly specific)
Anti-histone (+ anti-ssDNA)	Drug-induced lupus
Ro, La	Sjögren's (Ro also SCLE + neonatal lupus)
U1-RNP	MCTD
Jo-1 (anti-histidyl-tRNA synthetase)	Polymyositis — ILD risk; anti-synthetase syndrome
Scl-70 (anti-topoisomerase I)	Diffuse cutaneous scleroderma
Anti-centromere	Limited cutaneous scleroderma (CREST) — 80–90%
Anti-PM/Scl	SSc–PM overlap
Anti-RNA polymerase	Scleroderma renal crisis (60%)
Lupus anticoagulant, anti-cardiolipin, anti-β2-GP	APS
cANCA (anti-PR3)	GPA (Wegener's) — >95%
pANCA (anti-MPO)	MPA; EGPA

Criteria / scores at a glance

ACR 1987 RA (4/7): morning stiffness ≥1 hr, ≥3 joints swollen, hand-joint swelling, symmetric swelling, hand-X-ray erosions/decalcification, rheumatoid nodules, abnormal RF (asterisked 4 must be present ≥6 weeks).
ACR/EULAR 2010 RA: 4 scored domains — joint involvement, serology, acute-phase reactants, symptom duration; entry = ≥1 joint with unexplained synovitis.
ACR SLE: 4 of 11.
Bohan & Peter PM/DM (5 pillars): proximal weakness + ↑ enzymes (CK/AST/ALT/LDH/aldolase) + abnormal EMG + muscle biopsy + rash (DM-specific).
Inflammatory back pain (4/5, back pain >3 months): onset <40 yr, insidious, improves with exercise, no improvement with rest, night pain.
GPA/Wegener's triad: ENT + lung + kidney (cANCA anti-PR3 >95%).
EGPA/Churg–Strauss (Lanham 1984): asthma + eosinophilia + systemic vasculitis (>2 extrapulmonary organs) (pANCA anti-MPO).
Reiter's triad: arthritis + urethritis + conjunctivitis.
HSP tetrad: palpable purpura + GIT + arthritis/arthralgia + renal (biopsy = perivascular IgA).
Behçet: recurrent oral ulcers (mandatory) + 2 of {genital ulcers, eye, skin, pathergy}.
Scleroderma renal crisis: new-onset BP >150/85 + eGFR fall ≥30% + ↑ creatinine + MAHA + hypertensive retinopathy + proteinuria/haematuria + oliguria/anuria + flash pulmonary oedema (biopsy = thrombotic microangiopathy).
ACR 1990 PAN: ≥3/10 criteria for classification.
ACR 2020 Gout: initiate ULT during flare (conditional, with NSAID/colchicine/steroid cover); continue ULT indefinitely.
FMF: clinical diagnosis — MEFV supports but cannot exclude.
Modified Schober's (AS): 15 → <20 cm = limited lumbar flexion.
Chest expansion (AS): normal 3–15 cm. SIJ stress: FABER (Flexion, Abduction, External Rotation). Cervical: occiput-to-wall / tragus-to-wall.
Glucocorticoid dose (prednisone-equiv/day): Low ≤7.5 · Medium >7.5–≤30 · High >30–≤100 · Very high >100 · Pulse ≥250 ×1 day / few days.
CRPS stages: 1 Acute 1–3 mo (warm/red, oedema) · 2 Dystrophic 3–6 mo (cold/cyanotic, osteoporosis) · 3 Atrophic late (contractures, waxy trophic skin).
Sensitivity vs specificity: high Sn → neg rules OUT (screening); high Sp → pos rules IN (confirmation).
WHO/ISN lupus nephritis: 1 normal LM · 2 mesangial · 3 focal proliferative · 4 diffuse proliferative · 5 membranous · 6 interstitial/tubular.
Sacroiliitis X-ray grade (0–IV): 0 normal · I suspicious/hazy · II erosions + sclerosis, joint space preserved · III narrowing + partial ankylosis · IV bilateral ankylosis (fusion).
Five PsA patterns: DIP 55–70% · asymmetric oligo (<5 joints) 30–50% · symmetric poly (RA-like) 15–70% · spondylitic 5–33% · arthritis mutilans 3–5%.
RA joint distribution: MCP/PIP/MTP 90% · knees/wrists/ankles 80% · hip/elbow 50% · cervical spine 40% · TMJ/AC 30% · cricoarytenoid 10%.
Vasculitis by vessel size: Large = GCA, Takayasu · Medium = PAN, Kawasaki · Small/medium (ANCA) = GPA, EGPA, MPA · Small = HSP, essential mixed cryoglobulinaemia · Variable = Behçet's.
Joint-count / timing: mono 1 · oligo 2–4 · poly ≥5; acute <14 days · subacute 2–6 wk · chronic >6 wk.
4 A's of AS (extra-articular): Anterior uveitis (40%), Aortic valve/root (AR), Apical fibrosis, Amyloidosis.
CREST: Calcinosis · Raynaud's · Oesophageal dysfunction · Sclerodactyly · Telangiectasia.
Five ocular of RA: keratoconjunctivitis sicca, episcleritis, scleritis, scleromalacia, scleromalacia perforans (corneal melt = most severe).
ANA pattern → association (next test): Homogeneous → SLE/MCTD (dsDNA) · Speckled → SLE/MCTD/Sjögren's (ENA) · Nucleolar → SLE/scleroderma (Scl-70) · Centromere → limited scleroderma/CREST · Cytoplasmic → myositis (Jo-1).
ESR/CRP: both high (rise together) = active inflammation (RA/vasculitis/infection) or drug reaction; ESR high + CRP normal = SLE, Sjögren's (polyclonal IgG), cancer.
CAN'T LEAP (under-excretion gout drugs): Cyclosporin, Alcohol, Nicotinic acid, Thiazides, Lasix, Ethambutol, Aspirin (low-dose), Pyrazinamide.
Hyperuricaemia: serum urate >6.8 mg/dl (>360 µmol/l).
Imaging cutoffs: OA = Kellgren–Lawrence 0–4; atlantodental interval (ADI) normal ≤3 mm adults / ≤5 mm children.

Discriminators that decide questions

Gout vs Pseudogout — Gout: MSU, needle, strongly negatively birefringent, yellow ∥ axis; X-ray = punched-out erosions with OVERHANGING edges + preserved joint space. Pseudogout: CPPD, rhomboid, weakly positively birefringent, blue ∥ axis; X-ray = chondrocalcinosis. (No crystal-dissolving therapy for CPPD, unlike gout.)
RA vs OA — RA spares DIP, symmetric small-joint, warmth + soft swelling, marginal erosions. OA involves DIP (vs RA spares DIP), "bony swellings" + crepitus, osteophytes + joint-space narrowing.
DM vs PM vs IBM — DM has rash (Gottron's pathognomonic, heliotrope); PM has NO rash (the key DM-vs-PM split); IBM = males >50, both proximal AND distal weakness, does NOT respond to steroids.
GPA vs EGPA vs MPA (ANCA vasculitides) — GPA: cANCA/anti-PR3 (>95%), ENT + lung + kidney. EGPA: pANCA/anti-MPO + asthma + eosinophilia. MPA: pANCA/anti-MPO, pauci-immune GN, distinguished from EGPA by NO asthma/eosinophilia.
Primary vs Secondary Raynaud's — Primary (good signs): teen/early-20s onset, stable, familial, normal capillaries, ANA−. Secondary (bad signs): male, ≥35 yr onset, increasingly severe, no FH, abnormal capillaries, ANA+/ENA+ (10–15% progress to defined CTD).