Rheumatoid Arthritis - MSK - Medbullets Step 1

Snapshot
A 36-year-old woman presents to her physician's clinic with pain and swelling in the hands and wrists. She reports morning stiffness that lasts for approximately 1 hour which later improves. She also states to be experiencing symptoms of depression and fatigue. On physican exam, there is decreased grip strength and 4/5 strength on wrist extension. There is tenderness to palpation and swelling of the proximal interphalangeal joints and metacarpophalangeal joints.
Introduction
Definition a chronic autoimmune disorder that primarily affects the joints and results in an inflammatory synovitis Epidemiology demographics sex more common in women age 30-50 years of age risk factors smoking Etiology environmental and genetic factors play a role Pathogenesis T- and B-cell response after a triggering event (e.g., infection in a genetically susceptible patient) eventually results in pannus formation and subsequent damage to the adjacent cartilage and bone Th1 cells release interferon-γ (IFN-γ) in order to activate macrophages and synovial cells Th17 cells secrete interleukin-17 (IL-17) in order to recruit monocytes and neutrophils synovial plasma cells produce antibodies against self antigens such as citrullinated peptides Genetics HLA-DR4 Associated conditions Sjogren syndrome Felty syndrome seropositive rheumatoid arthritis with neutropenia many patients have splenomegaly Caplan syndrome seropositive rheumatoid arthritis with pneumoconiosis Prognosis certain patients with early rheumatoid arthritis may achieve remission
Presentation
Symptoms fatigue and depression morning stiffness that lasts > 1 hour pain, stiffness, and/or swelling of the joint such as the metacarpophalangeal (MCP) joints proximal interphalangeal (PIP) joints metatarsophalangeal (MTP) joints Physical exam anemia of chronic disease weight loss decreased grip strength palmar erythema subcutaneous (rheumatoid) nodules splenomegaly in cases of Felty syndrome ulnar deviation of the fingers swan neck deformity bouttoniere deformities

Imaging
Radiography indications can be obtained during the initial workup to have a baseline to compare to when following disease progression can be performed of the neck to rule out odontoid ligament laxity modality hands, wrists, and feet findings diffuse osteopenia joint space narrowing in the carpal, metacarpal, phalangeal, and interphalangeal joints periarticular bony erosions ulnar deviation of the fingers
Studies
Labs rheumatoid factor (RF) antibody testing RF is an IgM antibody that targets the Fc portion of IgG anti-CCP antibody testing more specific for rheumatoid arthritis erythrocyte sedimentation rate (ESR) levels typically elevated C-reactive protein (CRP) levels typically elevated Diagnostic criteria diagnosis is based on clinical presentation and laboratory studies

Differential

Systemic lupus erythematous
Psoriatic arthritis
Scleroderma
Polymyalgia rheumatica
Gout

Treatment

Conservative
- education, exercise, physical therapy, vaccinations, smoking cessation, and counseling
  - indication
    - a component of treatment for patients with rheumatoid arthritis
Pharmacologic
- disease-modifying antirheumatic drugs (DMARDs)
  - indications
    - used to prevent, stop, or retard disease-associated damage
  - medications
    - methotrexate
      - typically the initial DMARD used
    - tumor necrosis factor (TNF) inhibitor such as
      - etanercept
      - adalimumab
    - leflunomide
    - sulfasalazine
    - hydroxychloroquine
- nonsteroidal antiinflammatory drugs (NSAIDs) and/or glucocorticoids
  - indications
    - initially given for symptomatic control while waiting for DMARD response
Operative
- joint replacement surgery
  - indication
    - in patients with severe joint damage or failure to respond to conservative and medical therapy

Complications

Hand deformities
Atlantoaxial subluxation
Popliteal cyst

Blood, Plasma, Serum	Reference Range
ALT	8-20 U/L
Amylase, serum	25-125 U/L
AST	8-20 U/L
Bilirubin, serum (adult) Total // Direct	0.1-1.0 mg/dL // 0.0-0.3 mg/dL
Calcium, serum (Ca²⁺)	8.4-10.2 mg/dL
Cholesterol, serum	Rec: < 200 mg/dL
Cortisol, serum	0800 h: 5-23 μg/dL //1600 h: 3-15 μg/dL 2000 h: ≤ 50% of 0800 h
Creatine kinase, serum	Male: 25-90 U/L Female: 10-70 U/L
Creatinine, serum	0.6-1.2 mg/dL
Electrolytes, serum
Sodium (Na⁺)	136-145 mEq/L
Chloride (Cl^-)	95-105 mEq/L
Potassium (K⁺)	3.5-5.0 mEq/L
Bicarbonate (HCO₃^-)	22-28 mEq/L
Magnesium (Mg²⁺)	1.5-2.0 mEq/L
Estriol, total, serum (in pregnancy)
24-28 wks // 32-36 wks	30-170 ng/mL // 60-280 ng/mL
28-32 wk // 36-40 wks	40-220 ng/mL // 80-350 ng/mL
Ferritin, serum	Male: 15-200 ng/mL Female: 12-150 ng/mL
Follicle-stimulating hormone, serum/plasma	Male: 4-25 mIU/mL Female: premenopause: 4-30 mIU/mL midcycle peak: 10-90 mIU/mL postmenopause: 40-250
pH	7.35-7.45
PCO₂	33-45 mmHg
PO₂	75-105 mmHg
Glucose, serum	Fasting: 70-110 mg/dL 2-h postprandial:<120 mg/dL
Growth hormone - arginine stimulation	Fasting: <5 ng/mL Provocative stimuli: > 7ng/mL
Immunoglobulins, serum
IgA	76-390 mg/dL
IgE	0-380 IU/mL
IgG	650-1500 mg/dL
IgM	40-345 mg/dL
Iron	50-170 μg/dL
Lactate dehydrogenase, serum	45-90 U/L
Luteinizing hormone, serum/plasma	Male: 6-23 mIU/mL Female: follicular phase: 5-30 mIU/mL midcycle: 75-150 mIU/mL postmenopause 30-200 mIU/mL
Osmolality, serum	275-295 mOsmol/kd H₂O
Parathyroid hormone, serume, N-terminal	230-630 pg/mL
Phosphatase (alkaline), serum (p-NPP at 30° C)	20-70 U/L
Phosphorus (inorganic), serum	3.0-4.5 mg/dL
Prolactin, serum (hPRL)	< 20 ng/mL
Proteins, serum

Hematologic	Reference Range
Bleeding time	2-7 minutes
Erythrocyte count	Male: 4.3-5.9 million/mm³ Female: 3.5-5.5 million mm³
Erythrocyte sedimentation rate (Westergren)	Male: 0-15 mm/h Female: 0-20 mm/h
Hematocrit	Male: 41%-53% Female: 36%-46%
Hemoglobin A1c	≤ 6 %
Hemoglobin, blood	Male: 13.5-17.5 g/dL Female: 12.0-16.0 g/dL
Hemoglobin, plasma	1-4 mg/dL
Leukocyte count and differential
Leukocyte count	4,500-11,000/mm³
Segmented neutrophils	54%-62%
Bands	3%-5%
Eosinophils	1%-3%
Basophils	0%-0.75%
Lymphocytes	25%-33%
Monocytes	3%-7%
Mean corpuscular hemoglobin	25.4-34.6 pg/cell
Mean corpuscular hemoglobin concentration	31%-36% Hb/cell
Mean corpuscular volume	80-100 μm³
Partial thromboplastin time (activated)	25-40 seconds
Platelet count	150,000-400,000/mm³
Prothrombin time	11-15 seconds
Reticulocyte count	0.5%-1.5% of red cells
Thrombin time	< 2 seconds deviation from control
Volume
Plasma	Male: 25-43 mL/kg Female: 28-45 mL/kg
Red cell	Male: 20-36 mL/kg Female: 19-31 mL/kg

Cerebrospinal Fluid	Reference Range
Cell count	0-5/mm³
Chloride	118-132 mEq/L
Gamma globulin	3%-12% total proteins
Glucose	40-70 mg/dL
Pressure	70-180 mm H₂O
Proteins, total	< 40 mg/dL

Sweat	Reference Range
Chloride	0-35 mmol/L
Urine
Calcium	100-300 mg/24 h
Chloride	Varies with intake
Creatinine clearance	Male: 97-137 mL/min Female: 88-128 mL/min
Estriol, total (in pregnancy)
30 wks	6-18 mg/24 h
35 wks	9-28 mg/24 h
40 wks	13-42 mg/24 h
17-Hydroxycorticosteroids	Male: 3.0-10.0 mg/24 h Female: 2.0-8.0 mg/24 h
17-Ketosteroids, total	Male: 8-20 mg/24 h Female: 6-15 mg/24 h
Osmolality	50-1400 mOsmol/kg H₂O
Oxalate	8-40 μg/mL
Potassium	Varies with diet
Proteins, total	< 150 mg/24 h
Sodium	Varies with diet
Uric acid	Varies with diet
Body Mass Index (BMI)	Adult: 19-25 kg/m²