Differentiating rheumatoid arthritis from other diseases

# Overview

# Differentiating Rheumatoid arthritis from other Diseases
- Osteoarthritis (OA):
Signs and symptoms of osteoarthritis are usually minimal and spares the wrist joint and the metacarpophalangeal joint. It typically affects the distal inter-phalangeal joint and frequently associated with Heberden's nodes.
Joint stiffness is usually minimal in OA and lasts less than one hour. In contrast, joint stiffness is a very prominent symptom of RA and should last more than an hour for atleast 6 weeks in order to fulfill the criteria for diagnosis defined by The American College of Rheumatology.
- Signs and symptoms of osteoarthritis are usually minimal and spares the wrist joint and the metacarpophalangeal joint. It typically affects the distal inter-phalangeal joint and frequently associated with Heberden's nodes.
- Joint stiffness is usually minimal in OA and lasts less than one hour. In contrast, joint stiffness is a very prominent symptom of RA and should last more than an hour for atleast 6 weeks in order to fulfill the criteria for diagnosis defined by The American College of Rheumatology.
- Systemic lupus erythematosus (SLE):
Symptoms specific to SLE like butterfly malar rash, Discoid lupus erythromatosus, photosensitivity, myositis, nephritis are not seen in RA.
The C reactive protein levels are often normal or mildly elevated in SLE, whereas it is always elevated in RA. However, the erythrocyte sedimentation rate is found to be elevated in both.
- Symptoms specific to SLE like butterfly malar rash, Discoid lupus erythromatosus, photosensitivity, myositis, nephritis are not seen in RA.
- The C reactive protein levels are often normal or mildly elevated in SLE, whereas it is always elevated in RA. However, the erythrocyte sedimentation rate is found to be elevated in both.
- Septic arthritis
Bacterial cause: Characterized by fever, chills, joint swelling and tenderness, demonstration of causative organism in the aspirated joint fluid by gram staining or microbial culture.
Viral cause: rubella, parvovirus B19, hepatitis B virus, hepatitis C virus are the most common responsible etiologic agents. The syndrome is often self limiting, lasting for a few weeks, and rarely beyond 6 weeks. Serology can help identifying HBV, HCV, parvovirus B19. Anti-CCP antibody is more specific than Rheumatoid factor for establishing a diagnosis of RA, as Rheumatoid factor levels may be raised in HCV infection.
Lyme Arthritis: It is characterized by intermittent, persistent or migratory pattern of arthritis, often involving large joints like knee, shoulder, ankle, elbow, wrist and temporomandibular joint in the decreasing order of incidence. Involvement of small joints of the hand is not common with Lyme disease. Diagnosis is made by serology. Other clues include residing in an endemic area, antecedent history of erythema chronicum migrans.
- Bacterial cause: Characterized by fever, chills, joint swelling and tenderness, demonstration of causative organism in the aspirated joint fluid by gram staining or microbial culture.
- Viral cause: rubella, parvovirus B19, hepatitis B virus, hepatitis C virus are the most common responsible etiologic agents. The syndrome is often self limiting, lasting for a few weeks, and rarely beyond 6 weeks. Serology can help identifying HBV, HCV, parvovirus B19. Anti-CCP antibody is more specific than Rheumatoid factor for establishing a diagnosis of RA, as Rheumatoid factor levels may be raised in HCV infection.
- Lyme Arthritis: It is characterized by intermittent, persistent or migratory pattern of arthritis, often involving large joints like knee, shoulder, ankle, elbow, wrist and temporomandibular joint in the decreasing order of incidence. Involvement of small joints of the hand is not common with Lyme disease. Diagnosis is made by serology. Other clues include residing in an endemic area, antecedent history of erythema chronicum migrans.
- Gout:
Chronic gout can assume a polyarticular pattern and can be confused with RA. However, demonstration of urate crystals in the aspirated joint fluid and presence of tophi on physical examination can help establish diagnosis.
- Chronic gout can assume a polyarticular pattern and can be confused with RA. However, demonstration of urate crystals in the aspirated joint fluid and presence of tophi on physical examination can help establish diagnosis.
- Polymyalgia rheumatica:
It often asymmetric, seen in those above 50 years of age, involves proximal muscles of shoulder and hip, and tends to have a milder course.
Stiffness involves the axial muscles more often than the small joints of hand that predominates RA.
They are typically seronegative or have only a mild elevation of Rheumatoid factor and respond dramatically to glucocorticoids.
- It often asymmetric, seen in those above 50 years of age, involves proximal muscles of shoulder and hip, and tends to have a milder course.
- Stiffness involves the axial muscles more often than the small joints of hand that predominates RA.
- They are typically seronegative or have only a mild elevation of Rheumatoid factor and respond dramatically to glucocorticoids.
- Paraneoplastic syndromes:
Hypertrophic pulmonary osteoarthropathy]]: Characterized by clubbing of digits, joint pain (deep and nagging type) and periosteal reaction.
Myelodysplastic syndrome: Patients with myelodysplastic syndrome often present with various autoimmune diseases including polyarthritis which could be confused with RA.
- Hypertrophic pulmonary osteoarthropathy]]: Characterized by clubbing of digits, joint pain (deep and nagging type) and periosteal reaction.
- Myelodysplastic syndrome: Patients with myelodysplastic syndrome often present with various autoimmune diseases including polyarthritis which could be confused with RA.
- Other differentials:
Fibromyalgia
Polychondritis
Psoriatic arthritis
Sarcoidosis
Sjogren syndrome
- Fibromyalgia
- Polychondritis
- Psoriatic arthritis
- Sarcoidosis
- Sjogren syndrome

# Differential diagnosis
Key:+ : Infrequently present, ++ : Frequently present, +++ : Always present, - : Absent
Key:+ : Infrequently present, ++ : Frequently present, +++ : Always present, - : Absent