Pathophysiology
1) acute, infectious, and highly contagious viral infection caused by Morbillovirus (Paramyxovirus) contacting the nasopharynx and bronchi 2) spread then occurs to regional lymph nodes and systemically
Signs and Symptoms
Usual presentation – 1) fever and malaise 2) cough 3) rhinorrhea 4) conjunctivitis Followed by – 5) small, punctate, bluish-white dots on a red base (Koplik spots) on throat and tongue 6) maculopapular rash starting on face at hairline and spreading to torso and limbs that lasts 3-4 days 7) pneumonia 8) croup 9) otitis media 10) enlarged cervical and mesenteric lymph nodes and splenomegaly 11) red lips
Characteristic Test Findings
Laboratory – 1) decreased WBC count 2) increased AST and ALT 3) increased protein in CSF 4) increased IL-4
Histology/Gross Pathology
1) single-stranded RNA virus 2) necrosis of affected airway epithelium with lymphocytes present 3) T lymphocytes react with virus particles, causing vasculitis in small vessels in skin 4) in affected lymph tissue fusion of cells into a giant multinucleated cell (up to 100 nuclei) with intranuclear and intracytoplasmic inclusions (Warthin-Finkeldey cells) 5) bronchiolar pneumonia and bronchiectasis if occurs in a population with little exposure
Associated Conditions
1) pneumonia 2) otitis media 3) CNS involvement with seizures, headaches, and drowsiness 4) myocarditis 5) hepatitis 6) transverse myelitis 7) subacute sclerosing panencephalitis (SSPE) is now very rare with modern vaccines
Biochemistry
rubeola virus has H and F proteins that allow virus particles to attach and fuse with respiratory epithelium
Inheritance/Epidemiology
1) incubation is 10-21 days 2) virus is shed before the patient exhibits symptoms 3) transmission is via respiratory aerosol 4) only known reservoir is humans 5) largely a disease of children 6) kills 1.5 million children worldwide 7) mortality rate is 10-25% if occurs in malnourished, ill, or very young patients 8) 500 cases/year in USA
Treatment
1) vaccination with, live attenuated virus is given in first 16 months of life as part of MMR vaccine (measles, mumps, rubella) 2) if disease occurs, care is supportive
Tips for USMLE
1) Warthin-Finkeldey giant cells are pathognomonic for measles 2) Koplik’s spots are pathognomonic for measles 3) the rash does not itch 4) three C’s of measles – conjunctivitis, cough, and coryza (runny nose)
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