Infectious Myositis Clinical Presentation

Updated: Jan 13, 2018
  • Author: Mohammed J Zafar, MD, FAAN, FACP, FASN; Chief Editor: Niranjan N Singh, MBBS, MD, DM, FAHS, FAANEM  more...
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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. A patient with trichinosis and ocular involvement. Courtesy of Centers for Disease Control and Prevention and Dr. Thomas F. Sellers, Jr.
    • 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