Infectious Myositis Clinical Presentation

See the list below:

• Key historical points should be confirmed.

  • Risk factors for Staphylococcus aureus pyomyositis - Strenuous activity, muscle trauma, skin infections, infected insect bites, illicit drug injections, connective tissue disorders, and diabetes

  • Overseas travel

  • Consumption of poorly cooked meats (especially pork products in the case of trichinosis or cysticercosis)

  • Tick bites

• Pyomyositis

  • Psoas abscess - Subtle symptoms such as fever and flank and hip pain; may manifest as pyrexia of unknown origin; may be primary (no identifiable source of infection/from occult hematogenous spread) or secondary (spread from infection in the vicinity)

  • Occur mostly in the immunocompromised

  • Fever and malaise

• Streptococcal myositis

  • Most common form is group A streptococci (GAS) necrotizing myositis/streptococcal myonecrosis

  • Usually seen in the men and young adults

  • Spontaneous occurrence (no history of penetrating trauma) or in the immunocompromised

• Trichinosis

  • Cardinal features - Myalgia, periorbital swelling, and fever (see following image)

    A patient with trichinosis and ocular involvement. Courtesy of Centers for Disease Control and Prevention and Dr. Thomas F. Sellers, Jr.

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  • Depending on site of involvement - Diplopia, dysarthria, dysphagia, dyspnea

• Lyme myositis

  • Pain and weakness of the proximal muscle groups

  • Symptoms in the vicinity of skin lesions or in limb muscles

• Cysticercosis with myositis - Fever, myalgias

• Trypanosomiasis with myositis

  • Acute stage

    • May be asymptomatic or characterized by fever

    • Myositis occurring in the early stage of infection - Symptoms such as muscle weakness and myalgias mimicking those of polymyositis

  • Chronic stage - Myalgias

• Toxoplasma myositis - Fever, myalgias, and muscle weakness

• Influenza myositis - Childhood and adult forms recognized

  • Childhood form

    • Fever, malaise, and rhinorrhea followed 1-7 days later by severe pain, especially in the calves

    • Muscle pain worse with movement, especially with walking

    • Symptoms of myositis - Generally last 1-7 days

  • Adult form

    • Fever, myalgias, generalized weakness

    • Muscle swelling in some patients

• Acute coxsackievirus myositis

  • Group A virus infection - Myalgias, weakness

  • Group B virus infection - Causes epidemic pleurodynia (Bornholm disease or epidemic myalgia), which is considered a form of myositis

    • This is an acute, febrile disorder with abrupt onset of pain in the abdomen or lower thoracic region.

    • Pain can be referred to the back and shoulders.

    • Pain is worse with movement, breathing, or coughing.

• Fungal myositis

  • Most often seen in severely immunosuppressed patients

  • Clinical presentation is similar to pyomyositis

• Cryptococcal myositis

  • Rare cause of myositis

  • Most involve immunocompromised patients.

  • Symptoms overlap those of bacterial myositis.

  • Often present with lower extremity pain and swelling

  • May involve the paraspinal musculature

See the list below:

• Pyomyositis

  • Muscles are painful, swollen, tender, and indurated.

  • Quadriceps muscle is involved most commonly.

  • The second most common location is the psoas muscle, followed by the upper extremities.

  • Depending on the site of involvement, it may mimic appendicitis (psoas muscle), septic arthritis of the hip (iliacus muscle), or epidural abscess (piriformis muscle).

  • This may be difficult to distinguish clinically from inflammatory myopathy.

  • Findings may be subtle in immunocompromised persons requiring a high index of suspicion for diagnosis.

• Streptococcal myositis

  • Prodrome - Flulike symptoms

  • Evolves to severe local muscle pain, swelling, and fever

  • Rapidly progressive and can be fatal

  • Complications - Bacteremia, toxic shock syndrome, multiorgan failure

• Trichinosis

  • Involvement of orbital muscles can result in diplopia and strabismus.

  • Dysarthria or dysphagia can result when tongue and pharyngeal muscles are affected.

  • Limb muscles usually are mildly involved.

  • Other manifestations include myocarditis and dyspnea from diaphragmatic involvement.

• Lyme myositis

  • Weakness and atrophy of the proximal muscle groups can occur, accompanied by local swelling and tenderness.

  • Muscle weakness may be a major presenting feature of this disease.

  • Rarely, late ocular involvement, including orbital myositis ^[4] , may occur.

• Cysticercosis with myositis

  • The most common sites of involvement are the skeletal and cardiac muscle, brain, and eyes.

  • When skeletal muscles are involved, palpable cysticerci (mature larvae) appear in subcutaneous tissues.

  • A notable feature of this type of myositis is muscle pseudohypertrophy, which may be seen in the tongue or calf muscles.

  • During the acute stage of disease, patients may have fever and muscle tenderness.

• Trypanosomiasis with myositis

  • The acute stage of the disease may be characterized by fever, lymphadenopathy, and hepatosplenomegaly.

  • At the site of the insect bite, local inflammation (involving subcutaneous tissues and muscle) results in a swelling known as a chagoma.

  • Contamination of the eyes produces unilateral periocular and palpebral edema with conjunctivitis and preauricular lymphadenopathy (Romaña).

  • Extraocular involvement is rare. It may present with features of subacute orbital myositis and may mimic an orbital tumor.

  • During the acute parasitemic stage, intense infection of the myocardium may occur, producing severe myocarditis and disturbances of cardiac conduction.

  • Clinical manifestations in the early stage of myositis include muscle weakness, tenderness, and erythema mimicking those of polymyositis and dermatomyositis.

  • Skeletal muscle may be involved in the chronic stage as well and can last for decades.

• Toxoplasma myositis

  • Muscle invasion by Toxoplasma gondii usually is seen in immunocompromised individuals with disseminated toxoplasmosis.

  • The clinical features are similar to those of polymyositis, with manifestations of fever and muscle weakness.

  • Polymyositis is a prominent feature even in the congenital form of toxoplasmosis.

• Influenza myositis ^{[5, 6]}

  • Muscle weakness, tenderness, and swelling

    • More severe in adults

    • Proximal muscles are affected predominantly.

    • In children, involvement of the gastrocnemius-soleus muscles causes calf pain and difficulties with walking (toe-walking, wide-based gait)

    • Complications include myocarditis and respiratory dysfunction.

• Acute coxsackievirus myositis

  • Group A virus

    • These viruses can cause an acute, diffuse inflammatory myopathy.

    • This may progress to rhabdomyolysis and myoglobinuria, leading to renal failure.

  • Group B virus infection (epidemic myalgia)

    • Muscle tenderness and swelling may be noted in some patients.

    • Relapses can occur 2 weeks to a few months after the initial presentation.

• Fungal myositis

  • Clinically presents with fever, rash, and muscle tenderness

  • Lower extremities are commonly involved.

Known pathogens include the following:

• Viral - HIV-1 (one of the most common causes of myositis), HTLV-1, cytomegalovirus, group B coxsackievirus (epidemic myalgia), influenza

• Bacterial -S aureus (most common, 70%); Streptococcus viridans; Streptococcus pyogenes; Streptococcus pneumoniae ^[7] ; Salmonella enteritidis; Klebsiella pneumoniae; Clostridium freundii; Bartonella; gram-negative organisms including Escherichia coli,Pseudomonas aeruginosa, Neisseria species , Yersinia species , Morganella morganii, and Citrobacter species

• Spirochetal -B burgdorferi

• Mycobacterial -Mycobacterium avium-intracellulare complex

• Parasitic -T gondii, Trichinella spiralis, Trichinella nativa (from eating bear meat), T nelsoni, T britovi, T pseudospiralis, Echinococcus granulosus, T solium, T cruzi, microsporidia

• Fungal -Cryptococcus neoformans, Candida species (especially Candida tropicalis, Candida krusei, Candida albicans) , Histoplasma capsulatum, Coccidioides species , Aspergillus species , Pneumocystis jiroveci, microsporidia (eg, Anncaliia algerae ^[8] ), Fusarium species, and Actinomyces species; less common are mucormycosis, Sporothrix schenckii, and Blastomyces dermatitidis