USMLE® Step 1 style questions USMLE
USMLE® Step 2 style questions USMLE
A 16-year-old boy is brought to the emergency department for evaluation of testicular pain and scrotal swelling. He had an episode of bilateral facial swelling along the jawline several days ago with associated fevers, headaches, and myalgias. The pain is worsened with movement. He has no dysuria. He is not sexually active. Records demonstrate his parents refused vaccinations throughout childhood. Temperature is 38.2°C (100.7°F), pulse is 98/min, and blood pressure is 122/84 mmHg. Physical examination reveals bilaterally enlarged and tender testicles. Stroking of the inner thigh bilaterally results in elevation of the testes. Which of the following is the most likely etiology of this patient’s clinical condition?
Content Reviewers:Rishi Desai, MD, MPH
Contributors:Tanner Marshall, MS
Mumps only affects humans and is spread by tiny respiratory droplets that are small enough to be carried short distances in the air, so mumps virus is extremely contagious and anyone near a person with mumps is at risk for getting the disease as well.
The mumps virus has a single strand of RNA and a viral polymerase enzyme surrounded by a phospholipid bilayer envelope studded with viral proteins hemagglutinin-neuraminidase, or HN protein, and fusion or F protein.
The HN protein allows the virus to stick to a potential host cell, and cut itself loose if necessary, and the F-protein which fuses the viral and cell membranes together allowing the mumps virus to enter the cell.
Once mumps enters a cell, the single stranded RNA, which is negative sense, gets transcribed by the viral polymerase enzyme, into a complementary positive sense strand of mRNA, which can then be translated by the host cell ribosomes into new copies of the envelope proteins and the viral polymerase, which get assembled into new viruses.
What also ends up happening with these, though, is that those HN and F-proteins on the cell surface now bind other cells, so they actually end up bind epithelial cells to one another, which forms a clump of connected cells called a multinucleated giant cell or a syncytium.
Mumps enters the body and first infects the epithelial cells of the nasopharynx, where it starts replicating and causing local damage to the tissue.
From there, it can cause viremia or virus in the blood, and reach various organs and tissues.
The mumps virus has tropism, or preference for, the parotid salivary glands, and the most classic finding in mumps is swelling of parotid salivary glands either on one side or on both sides, sometimes with an associated earache.
The swollen parotid gland lifts the earlobe up and out and obscures the angle of the jaw, and can sometimes cause trismus which is spasm of the muscles of mastication or chewing.
Mumps also has affinity for the central nervous system, and can cause meningitis, which is an infection of the lining of the brain, as well as encephalitis, which is an infection of the brain tissue itself.
These infections can cause symptoms ranging from those that feel like the common cold, like headache and neck stiffness, as well as more severe symptoms like difficulty with balance and hearing loss, but in general, the infection is self-limited and symptoms go away as the body recovers.