Understanding Reactive Arthritis and Differential Diagnosis

Reactive arthritis is a condition characterized by the presence of urethritis, arthritis, and conjunctivitis. It typically occurs 1-3 weeks after an initial infection, with Chlamydia trachomatis and Salmonella, Shigella, and Campylobacter being the most common causative agents. In addition to the classic triad of symptoms, patients may also experience keratoderma blennorrhagica and buccal and lingual ulcers.

When considering differential diagnoses, it is important to note that inflammatory arthritides can be seropositive or seronegative. Seronegative spondyloarthritides include ankylosing spondylitis, psoriatic arthritis, enteropathic arthritis, reactive arthritis, and gonococcal arthritis.

Gonococcal arthritis is a form of septic arthritis that typically affects a single joint and presents with a hot, red joint and systemic signs of infection. Ankylosing spondylitis, on the other hand, does not present with any clinical features in this patient. Enteropathic arthritis is associated with inflammatory bowel disease, which is less likely in a patient with a recent history of travel and diarrhea. Psoriatic arthritis is unlikely to present simultaneously with psoriasis in a young, previously healthy patient without any prior history of either condition.

When it comes to bone density, T scores are an important measure to understand. A T score of less than -2.5 is indicative of osteoporosis, while a T score between -1 and -2.5 suggests osteopenia. On the other hand, a T score of 0-1 is considered normal, but may still require monitoring. A T score greater than 2.5 is also normal, but may not be the case if the patient has experienced a fragility fracture. It’s important to note that Z scores, which take into account age and gender, can also provide insight into bone density. Understanding T scores and their implications can help healthcare professionals and patients take preventative measures to maintain bone health.

Treatment Options for Severe Rheumatoid Arthritis

Severe rheumatoid arthritis can be a challenging condition to manage, especially when conventional disease-modifying anti-rheumatic drugs (DMARDs) fail to provide relief. In such cases, biological therapies may be recommended. Here are some treatment options for severe rheumatoid arthritis:

Enrol in Biological Therapy Programme
Patients with highly active disease despite trying three previous agents for a therapeutic treatment duration may be candidates for biological treatments. TNF-alpha inhibitors and anti-CD20 are examples of biological treatments that are routinely used in the UK.

Maintain on Steroids and Add a Bisphosphonate
Short-term treatment with glucocorticoids may be offered to manage flares in people with recent-onset or established disease. However, long-term treatment with glucocorticoids should only be continued when the long-term complications of glucocorticoid therapy have been fully discussed and all other treatment options have been offered.

Commence Leflunomide
Severe disease that has not responded to intensive therapy with a combination of conventional DMARDs should be treated with biological agents. Leflunomide is one of the DMARDs that can be used in combination therapy.

Use Methotrexate/Leflunomide Combination
Patients who have not responded to intensive DMARD therapy may be prescribed a biological agent, as per NICE guidelines. Methotrexate and leflunomide are two DMARDs that can be used in combination therapy.

Avoid Commencing Penicillamine
DMARD monotherapy is only recommended if combination DMARD therapy is not appropriate. Patients without contraindications to combination therapy should not be prescribed penicillamine.

Osteoarthritis in the Hand and Elbow

Osteoarthritis (OA) is a prevalent form of arthritis that commonly affects the hand, particularly the joints. The joints may exhibit several deformities, including the development of small bone spurs called nodes. These nodes are referred to as Heberden’s nodes when they occur at the joint next to the fingernail and Bouchard’s nodes when they occur at the middle joints. The base of the thumb may also appear squared off, accompanied by swelling and tenderness. Soft tissue laxity can result in instability at the base of the thumb.

In contrast, elbow OA is relatively uncommon.

Differential diagnosis for a patient with rheumatoid arthritis, splenomegaly, neutropenia, and skin changes

Felty syndrome and other potential diagnoses

Felty syndrome is a rare complication of rheumatoid arthritis that affects about 1% of patients. It is characterized by the presence of three main features: splenomegaly (enlarged spleen), neutropenia (low white blood cell count), and recurrent infections. Skin changes on the lower limbs, such as ulcers or nodules, are also common in Felty syndrome. The exact cause of this syndrome is unknown, but it is thought to be related to immune dysregulation and chronic inflammation.

Other conditions that may present with similar symptoms include chronic lymphocytic leukemia (CLL), non-Hodgkin’s lymphoma, Hodgkin’s lymphoma, and drug-induced neutropenia. CLL is a type of blood cancer that affects mainly older adults and causes the accumulation of abnormal lymphocytes in the blood, bone marrow, and lymph nodes. However, in this case, the patient’s white blood cell count is low, which is not typical of CLL. Non-Hodgkin’s lymphoma and Hodgkin’s lymphoma are types of cancer that affect the lymphatic system and may cause lymphadenopathy (enlarged lymph nodes), fever, night sweats, and weight loss. However, there is no evidence of lymph node involvement or systemic symptoms in this scenario.

Drug-induced neutropenia is a potential side effect of methotrexate, which is a commonly used medication for rheumatoid arthritis. However, splenomegaly is not a typical feature of methotrexate toxicity, and respiratory complications are more common than hematological ones. Therefore, the most likely diagnosis in this case is Felty syndrome, which requires close monitoring and management of the underlying rheumatoid arthritis. In severe cases, splenectomy (surgical removal of the spleen) may be considered to improve neutropenia and reduce the risk of infections.

Differentiating Systemic Lupus Erythematosus from Other Connective Tissue Diseases

Systemic lupus erythematosus (SLE) is a complex autoimmune disease that can present with a variety of symptoms. Patients may experience pleuritic chest pain, arthralgia, and a typical rash, which are all indicative of SLE. Anti-nuclear antibodies are typically positive, although they are not specific to lupus. Treatment for SLE involves glucocorticoids as the mainstay, with second-line agents including cyclophosphamide, hydroxychloroquine, and azathioprine. BLyS inhibitors are also showing promise in clinical trials.

Other connective tissue diseases, such as granulomatosis with polyangiitis (GPA), rheumatoid arthritis, systemic sclerosis, and mixed connective tissue disease, have distinct features that differentiate them from SLE. GPA is a necrotising small-vessel vasculitis that commonly affects the kidneys and lungs, with palpable purpura on the extremities. Rheumatoid arthritis typically presents with joint pain and swelling, but without a butterfly rash or hypertension. Systemic sclerosis affects the skin on the face, forearms, and lower legs, with Raynaud’s, sclerodactyly, and telangiectasia. Mixed connective tissue disease has features of SLE, but without any other connective tissue disease symptoms.

It is important to differentiate between these diseases to provide appropriate treatment and management for patients.

Polymyalgia rheumatica is an inflammatory disease that causes pain and stiffness in the shoulder and pelvic girdle muscles, along with systemic symptoms such as fever and weight loss. It is often associated with giant cell arthritis. Diagnosis can be difficult, but response to a moderate dose of steroids is a useful indicator. Non-steroidal anti-inflammatories are not recommended. Other inflammatory conditions should be excluded, such as rheumatoid arthritis, systemic lupus erythematosus, polymyositis, and polyarteritis nodosa.

Acid-Base Disorders and Differential Diagnosis of Granulomatosis with Polyangiitis

In cases of metabolic acidosis with respiratory compensation, the primary issue is a decrease in bicarbonate levels and pH, which is accompanied by a compensatory decrease in pCO2. On the other hand, respiratory acidosis with metabolic compensation is characterized by an increase in pCO2 and a decrease in pH, which is accompanied by a compensatory increase in bicarbonate levels.

When nosebleeds are present, the diagnosis of Granulomatosis with polyangiitis is more likely than microscopic polyarteritis due to upper respiratory tract involvement. Goodpasture’s disease is less likely because it does not cause a rash. In particular, 95% of patients with Granulomatosis with polyangiitis develop antineutrophil cytoplasmic antibodies (cytoplasmic pattern) or cANCAs, with proteinase-3 being the major c-ANCA antigen. Conversely, perinuclear or p-ANCAs are directed against myeloperoxidase, are non-specific, and are detected in various autoimmune disorders.

Sites of Crystal Deposition in Pseudogout

Pseudogout is a condition characterized by the deposition of calcium pyrophosphate dihydrate (CPPD) crystals in various tissues of the body. The most common site of deposition is the synovial fluid, which can lead to joint inflammation and pain. However, CPPD crystals can also be deposited in other tissues such as cartilage, ligaments, tendons, and bursae.

Cartilage is another common site for CPPD crystal deposition, and pseudogout is also known as chondrocalcinosis. Deposition in the ligaments and tendons is possible but less common than in the synovium. Bursae deposition is also possible but less common than synovium deposition.

In summary, while CPPD crystals can be deposited in various tissues in pseudogout, the synovium is the most common site of deposition, followed by cartilage, ligaments, tendons, and bursae.

Characteristics of Different Arthritis Types

Psoriatic arthritis is a type of arthritis that commonly affects the distal interphalangeal (DIP) joints. It is often accompanied by psoriasis around the adjacent nail, and other joint involvement is typically more asymmetric than in rheumatoid arthritis. On the other hand, Reactive arthritis is characterized by uveitis, urethritis, and arthritis that does not involve the DIP. Gout, another type of arthritis, does not typically affect the DIP either. While rheumatoid arthritis can occasionally affect the DIP, it is classically a MCP and PIP arthritis. Lastly, bursitis is a pathology of the bursa, not the joint itself. the characteristics of different types of arthritis can aid in proper diagnosis and treatment.