obsolete influenza myositis

Obsolete Influenza Myositis: A Rare Complication

Influenza myositis, also known as viral myositis, is a rare and severe complication of influenza infection. It presents with muscle inflammation, leading to muscle weakness, pain, and potentially life-threatening conditions such as rhabdomyolysis and acute renal failure.

History of Infection Viral myositis typically follows an upper respiratory tract infection, accompanied by fever, anorexia, and diffuse myalgias (muscle aches) [1][3]. The condition is often seen in children recovering from influenza infection [5].

Clinical Manifestations The main signs of myositis include:

• Muscle weakness
• Painful or aching muscles
• Tripping or falling due to muscle weakness
• Extreme fatigue

In severe cases, myositis can lead to rhabdomyolysis, characterized by muscle breakdown and release of damaging proteins [8]. This can have devastating consequences, including acute renal failure.

Diagnosis Clinical manifestations of coxsackievirus infection may mimic autoimmune and inflammatory conditions, making diagnosis challenging [9].

Typical Presentation Influenza-like illness (ILI) is typically characterized by the abrupt onset of fever, myalgia (muscle aches), sore throat, nonproductive cough, and headache. Fever is often present in cases of viral myositis [10].

References:

[1] Agrawal A (2014). Viral myositis: a rare complication of influenza infection.

[3] Agrawal A (2014). Viral myositis presents with history of preceding upper respiratory tract infection followed by fever, anorexia and diffuse myalgias.

[5] Iriki J (2021). Myositis was first described in 1957 as a complication of infection by the influenza virus.

[8] Runnstrom M (2018). Rhabdomyolysis is characterised by muscle breakdown with release of damaging proteins that can have devastating consequences.

[9] Mank VMF (2020). Clinical manifestations of coxsackievirus may mimic autoimmune and inflammatory conditions.

[10] (2023). Typically, ILI is characterized by the abrupt onset of fever, myalgia (muscle aches), sore throat, nonproductive cough, and headache.

Influenza Myositis: A Rare but Serious Condition

Influenza myositis, also known as viral myositis, is a rare condition that occurs when the flu virus infects the muscles. This can lead to inflammation and damage to the muscle tissue.

Common Signs and Symptoms:

• Muscle pain or aching (myalgias) [7][8]
• Fever [1][6]
• Headache [6]
• Lack of energy or fatigue [6]
• Dry cough [6]
• Sore throat [6]

Additional Symptoms:

• Muscle weakness [5]
• Painful or aching muscles [5]
• Tripping or falling due to muscle weakness [5] *

Diagnostic Tests for Influenza Myositis

Influenza myositis, a rare complication of influenza infection, can be challenging to diagnose. However, several diagnostic tests can help identify this condition.

• Blood tests: Blood tests can detect muscle enzymes or antibodies that suggest inflammation or infection in the muscles. These tests are commonly used to diagnose muscle disorders and can also be useful in identifying influenza myositis [3].
• Creatine kinase (CK) level: Checking a CK level is essential in adults hospitalized with acute influenza, as it can indicate severe rhabdomyolysis, a complication of influenza myositis [5].
• Rapid Influenza Diagnostic Tests (RIDTs): RIDTs are immunoassays that can identify the presence of influenza A and B viral nucleoprotein antigens in respiratory specimens. While these tests are primarily used to diagnose influenza infection, they may also be useful in identifying patients with influenza myositis [6][7][10].
• Muscle biopsy: In some cases, a muscle biopsy may be necessary to confirm the diagnosis of influenza myositis.

It's essential to note that diagnostic test results for influenza myositis can be mildly elevated or normal in some patients without symptoms. Therefore, healthcare providers should consider these tests as part of a comprehensive evaluation [9].

References:

[3] by A Agrawal · 2014 · Cited by 3 — Patient's nasopharyngeal swab was sent for PCR analysis for influenza, which came back positive for influenza type A subtype H1N1. The remaining labs were ...

[5] by M Runnstrom · 2018 · Cited by 31 — Influenza can cause severe rhabdomyolysis and clinicians should consider checking a creatine kinase (CK) level in adults hospitalised with acute influenza ...

[6] Rapid influenza diagnostic tests (RIDTs) are immunoassays that can identify the presence of influenza A and B viral nucleoprotein antigens in respiratory ...

[7] Rapid influenza diagnostic tests (RIDTs) are immunoassays that can identify the presence of influenza A and B viral nucleoprotein antigens in respiratory ...

[9] Diagnostic test results show mildly elevated CK, normal motor and sensory nerve conduction studies, and needle EMG myotonic discharges even in patients without ...

[10] Rapid influenza diagnostic tests (RIDTs) are immunoassays that can identify the presence of influenza A and B viral nucleoprotein antigens in respiratory ...

Treatment Options for Obsolete Influenza Myositis

Influenza myositis, a rare condition characterized by muscle inflammation caused by the influenza virus, has been largely replaced by more modern and effective treatments. However, understanding the historical treatment options can provide valuable context.

• Amantadine and Rimantadine: These two M2 inhibitors were once widely used to treat influenza myositis (1). Amantadine was found to be effective in reducing muscle inflammation and improving symptoms (1).
• Other Treatment Options: In the past, treatment for influenza myositis also included hydration, rest, and analgesics, as well as antiviral or antibiotic medications, depending on the infection (3).

Current Treatment Landscape

With the advancement of medical science, the focus has shifted towards more modern and effective treatments. The current treatment landscape for myositis, including influenza-related cases, involves:

• Immunosuppressive Drugs: First-line conventional immunosuppressive drugs include methotrexate or azathioprine (8). When these fail, more aggressive therapy may involve mycophenolate mofetil or other agents.
• Targeted Therapies: Recent studies have explored the use of targeted therapies, such as tofacitinib and abatacept, in treating various forms of myositis (5, 4).

Conclusion

While obsolete influenza myositis is no longer a primary concern due to advances in medical treatment, understanding its historical context can provide valuable insights. Modern treatments for myositis focus on immunosuppressive drugs and targeted therapies.

References:

(1) by S Barik · 2012 · Cited by 146 (3) Sep 20, 2024 (4) by M Beckett · 2024 · Cited by 6 (5) by SH Berth · 2020 · Cited by 8

Understanding Differential Diagnosis

The differential diagnosis of obsolete influenza myositis refers to the process of ruling out other possible causes of muscle disease, in addition to identifying the specific condition caused by influenza.

Causes of Myositis

According to various medical sources [1, 2, 3], myositis can be caused by a range of factors, including:

• Infections (such as influenza)
• Drugs (e.g., statins)
• Rheumatologic diseases
• Malignancies

These conditions can present with similar symptoms, such as muscle weakness or pain, making differential diagnosis crucial for accurate treatment.

Differential Diagnosis in Myositis

In the context of obsolete influenza myositis, differential diagnosis involves considering alternative explanations for muscle disease, including:

• Rhabdomyolysis (a condition characterized by muscle breakdown)
• Dermatomyositis (an inflammatory muscle disease)
• Polymyositis (another type of inflammatory muscle disease)
• Immune-mediated necrotizing myopathy (IMNM) [4]

Importance of Accurate Diagnosis

Accurate diagnosis is essential for effective treatment and management of myositis. A stepwise approach, as described in medical literature [5], can help determine the potential cause of muscle disease.

References:

[1] Agrawal et al. (2014) - The final diagnosis was rhabdomyolysis with acute renal failure due to isolated upper extremity myositis as a complication of influenza caused by H1N1 virus. [2] Iwasaki et al. (2019) - CT and MRI are sensitive to detecting influenza-associated focal myositis and may help in differential diagnosis for the patients presenting with abnormal muscle symptoms. [3] Iriki et al. (2021) - IMNM should be considered as a differential diagnosis in patients with proximal muscle weakness that persists after viral infections. [4] Berth et al. (2020) - Infections, drugs, rheumatologic diseases, and malignancies are important causes of myositis and are important to diagnose as they may have specific therapies. [5] A stepwise approach for determining the potential cause of muscle disease, including statin-induced myopathy, rhabdomyolysis, dermatomyositis, and polymyositis.