Influenzal acute myositis in the elderly

The Neurologic Manifestations of Coronavirus Disease 2019

The coronavirus disease 2019 (COVID-19) is an ongoing global pandemic that has so far affected 216 countries and more than 5 million individuals worldwide. The infection is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). While pulmonary manifestations are the most common, neurological features are increasingly being recognized as common manifestations of the COVID-19, especially in the cases of severe infection. These include acute cerebrovascular disease, encephalitis, and Guillain-Barre syndrome (GBS). Here, we review the neuropathogenesis of SARS-CoV-2 and the central and peripheral nervous system manifestations of COVID-19.

Neurologic aspects of influenza viruses

Although influenza A and B viruses are primarily known as respiratory viruses and mainly infected only the upper respiratory tract in humans, patients with influenza often develop signs and symptoms that are not due to the respiratory system. Frequently individuals with influenza develop headaches, meningismus, and even seizures in addition to their typical respiratory symptoms. In the past decades, influenza viruses have also been associated with serious non-respiratory signs. The famous 1918 strain of influenza was associated with von Economo's encephalitis lethargica and postencephalitic parkinsonism. In the 1960s influenza virus infections in children were associated with Reye's syndrome characterized often by fatty non-inflammatory hepatic disease and an encephalopathy with marked non-inflammatory cerebral edema. Intermittently children with influenza develop focal myalgia and myositis. Guillain–Barré syndrome was epidemiologically associated with the 1978 killed influenza vaccine but not subsequent vaccines. Although occasional children with influenza have developed encephalopathy, from 2000 through 2004 there was an increase in the number of serious cases of acute necrotizing encephalopathy accompanying infection with the influenza A 2009 strain. The current H5N1 strain of bird influenza occasionally infects humans with a high mortality rate and some appear to have central nervous signs. This chapter explores what is known about these influenza neurologic associations.

Experimental influenza B viral myositis

To investigate the pathogenesis of influenza myositis in animals, juvenile BALB/c mice were inoculated with influenza B/Lee virus intramuscularly into the right quadriceps muscle. Chicken normal allantoic fluid (NAF) or phosphate-buffered saline (PBS) was injected into the left quadriceps of control mice and in some virus-infected mice. Serum creatinine phosphokinase (CPK) levels rose significantly on days 1 and 2 post-inoculation (PI) in only virus-inoculated mice. On days 2 and 3 PI, right quadriceps muscles developed scattered foci of a predominantly mononuclear inflammation in the perimysial connective tissue often adjacent to degenerating or necrotic muscle fibers. Immunofluorescent staining with specific anti-influenza B virus antisera showed muscle fibers that contained specific staining in nuclei and adjacent cytoplasm. Skip areas of staining within muscle fibers suggested that not all muscle nuclei within an individual muscle fiber were infected. A continuous fall in infectious virus titer in the right quadriceps muscles suggested the initial virus inoculum became inactivated and progeny virions were not produced. Left quadriceps muscle never had muscle necrosis or endomysial inflammation, specific staining of viral antigen, virus isolation, or viral RNA detected by the reverse transcriptase polymerase chain reaction assay. These findings support the hypothesis that a non-permissive influenza viral infection can develop in murine skeletal muscle that can damage specific nuclear domains of muscle fibers producing muscle degeneration or necrosis. A similar type of muscle infection may develop in humans that occasionally develop focal myositis during influenza.

Two cases of acute myositis associated with influenza A virus infection in the elderly

During the influenza epidemic of 1998-1999, we observed two elderly patients with influenza-like symptoms who had evidence of acute myositis with elevated serum enzymes. Influenza A infection was confirmed serologically in either case. The present cases suggest that it is important to distinguish influenzal myositis from other forms of myopathy in the elderly patients.

Benign acute childhood myositis in Kuwait

Ten children, three girls and seven boys, aged 4-10 years, were admitted with benign acute childhood myositis during spring and winter months (March 1988 to March 1990). They presented with an acute onset of symmetrical calf muscle pain and tenderness, weakness and inability to walk a few days after a flu-like illness. All had raised serum creatine kinase and a normal erythrocyte sedimentation rate, and the majority had low peripheral white blood cell counts with relative lymphocytosis. Serum aspartate aminotransferase, alanine aminotransferase and lactate dehydrogenase were found to be raised in four patients. Virological studies performed in six children gave negative results. Full clinical recovery was achieved within 1-7 days. One child developed a second episode. These ten cases of benign acute childhood myositis are the first to be reported from this region.

Myalgia cruris epidemica (benign acute childhood myositis) associated with a Mycoplasma pneumonia infection

We report the case of a 6-year-old boy who presented with difficulty ambulating and an elevated creatinine phosphokinase level following an upper respiratory tract infection. Crural myositis was diagnosed; convalescent serum was negative for viruses, but demonstrated significant titers to Mycoplasma pneumoniae. Benign acute crural myositis has not heretofore been associated with Mycoplasmal infection.

Infectivity of influenza B virus in cultured human muscle

Severe muscle symptoms, particularly in children, are frequently associated with influenza B virus infection. In this study we examined the effects of influenza B virus (Lee Strain) on cultured human muscle by light and electron microscopy (EM), immunofluorescence, hemadsorption and plaque assays. Muscle injury was also evaluated by the appearance of muscle-specific creatine kinase (CK) in the culture medium. By fluorescence immunocytochemistry viral antigen was demonstrated in muscle cell nuclei within 3 h postinoculation (p.i.) and in the cytoplasm at 6 h p.i. Membrane-associated viral antigen was seen at 16 h p.i., at which time budding influenza virus-like particles could be demonstrated by EM, both in myoblasts and multinucleated myotubes. At 16 h all cells were hemadsorption positive. Plaque assays showed peak virus production at 48 h (p.i.), at which time cytopathic effects (cell retraction, pycnosis and cytoplasmic vacuolization) were prominent and some cells detached from the substratum. Leakage of muscle-specific CK isozyme into the culture medium could be demonstrated as early as 6 h p.i. with peak enzyme activity around 40-48 h p.i. Cytopathic changes and virus production were observed both in myoblasts and myotubes indicating that both cell types are susceptible.

The inflammatory myopathies

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