Dear Doctors: I had rheumatic fever when I was 5 years old. My heart is fine, but after my illness, I had trouble learning. I’m 79 now and still struggle to understand some things, especially the age we live in, with electronic everything. What does rheumatic fever do to the body? Can it affect the brain?

Dear Reader: Rheumatic fever is a complex disease that can develop when a strep infection goes untreated. This infection typically is strep throat, and sometimes it is scarlet fever. Both are caused by infection with group A streptococcal bacteria.

Rheumatic fever occurs mainly in children from 5 to 15 years old, and it usually causes symptoms one to five weeks after infection. When faced with an ongoing strep infection, the child’s immune system can go into overdrive. But instead of targeting just the bacteria, it attacks the body’s own tissues, as well. For this reason, rheumatic fever is regarded as an autoimmune disease. Although the reasons why this occurs are not fully understood, researchers believe that certain molecular features of group A streptococcal bacteria trick the body into attacking its own tissues. This is a mechanism known as molecular mimicry.

Because rheumatic fever affects the heart, blood vessels, joints, skin and brain, it has a wide range of symptoms. These include fever; pain, swelling, heat and tenderness in the joints of the elbows, wrists, ankles and knees; a distinctive rash; shortness of breath; chest pain; a racing heartbeat; weakness; and persistent fatigue.

You asked in your letter about the effect of rheumatic fever on your brain, but also said that your family doctor’s primary worry was about the health of your heart. His concern is well-founded. Although the word “rheumatic” refers to inflammation of the joints, connective tissues and muscles, the disease often adversely affects the heart. Widespread inflammation can do damage to the heart muscle and the heart’s valves.

While heart issues are seen as a primary risk of rheumatic fever, the disease also can affect the brain. Neurological symptoms include a disorder known as Sydenham chorea, which can appear up to six months after the infection has cleared. It’s estimated to occur in up to one-fourth of cases of rheumatic fever, and affects girls more often than boys. Symptoms can be both physical and cognitive, and can range from mild to severe. They include muscular weakness; jerky, uncoordinated movement; facial tics; slurred speech; and a stumbling gait. Some patients have trouble with reading and writing, and they may experience anxiety or emotional instability.

Although most children recover completely, in rare cases the condition can persist or recur. There is some evidence of a link between recurrent cases of Sydenham chorea and the later development of obsessive-compulsive disorder, autism and attention deficit/hyperactivity disorder. Up to 80% of those with Sydenham chorea also develop myocarditis, which is inflammation of the heart.

So much time has elapsed since your original illness, it would be difficult to say if Sydenham chorea has played a role in your life. One thing we can assure you of, however, is that when it comes to the complexities of the digital world, you are not alone in feeling a bit overwhelmed.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctors: The news here in Atlanta is talking about a new tick disease called the heartland virus. Our family spends a lot of time outdoors, so it’s something we’re worried about. What can you tell us about it? It seems like ticks are a bigger problem every year.

Dear Reader: Due to the mild climate in your part of the country, ticks are a year-round concern. And with spring weather warming much of the rest of the nation, regions that get a winter respite from the tiny parasites are seeing their return.

There are more than 80 species of ticks in the United States. Only a handful -- biologists estimate from 10 to 12 species -- commonly bite humans. That still poses a danger because, as most of us know, tick bites can transmit parasites, bacteria and viruses.

In recent years, the geographic range of various tick species has been expanding. This has led to a jump in the number of tick-borne infections reported each year. At the same time, biologists continue to identify new pathogens carried by ticks that cause disease in humans. Among these is the heartland virus that you’re asking about.

Different species of ticks carry different diseases. For the heartland virus, it’s the Lone Star tick. It’s a reddish-brown tick with a rounded body. Adults are about one-quarter of an inch long. Females have a white splotch on their backs, the so-called “Lone Star.” In males, white markings at the edges of the body resemble a horseshoe. It inhabits the southeastern, south-central and eastern states and is the most common tick in Georgia.

We have previously written about how a bite from a Lone Star tick can lead to alpha-gal syndrome, in which the person who was bitten becomes allergic to red meat. Now, researchers at Emory University in Atlanta have found that the Lone Star tick has become a potential carrier of the heartland virus. It’s a rare disease, with about 50 cases identified since its discovery in Missouri in 2009. However, as is common with diseases that health care providers aren’t familiar with yet, the actual number of cases is probably higher.

Symptoms are in line with other tick-borne diseases, including fever, headache, nausea, diarrhea, fatigue and muscle or joint pain. Diagnosis is via a patient's physical symptoms, their history of tick exposure and appropriate laboratory tests. There are no vaccines or medications to prevent or treat infection with heartland virus. Instead, patients receive supportive care that addresses their symptoms.

The best defense is to protect yourself. A tick perches on a bit of vegetation, legs outstretched, and waits for a host to brush up against it. So cover up when outdoors, preferably in light-colored clothes, which make ticks more visible. Be vigilant about checking your clothes, hair and skin for ticks when you return from an outing. And be sure to check your pets.

If bitten, use tweezers to grasp the tick as close to the skin as possible. Remove with a steady, even pressure, then clean the area with soap and water. If symptoms develop, it’s vital to seek medical care.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctors: I was walking our dog at night and didn’t see a big hole in the sidewalk. I stepped right into it, full force, and I think my knee actually bent backwards. I can walk OK, but now my knee hurts. Could I have damaged something? How do I know if I need to see my doctor?

Dear Reader: From your description of the incident, it sounds as though you hyperextended your knee. That means your knee joint was forced backward, just as you described, opposite of the direction in which it is designed to move. Depending on the force of the impact, and the degree to which the knee over-straightened, this can result in damage to the ligaments that stabilize the joint.

Let’s start with a closer look at the knee itself. It’s the largest joint in the body, and it is a remarkable feat of engineering. It functions as a hinge, allowing the lower leg to flex and extend. The knee joint links together the thigh bone, or femur, and the tibia, which is the larger bone in your shin. It also includes the kneecap, or patella, which is the small, rounded bone that forms a protective cap at the front of the joint. A series of internal and external ligaments weave their way through the joint capsule. They not only connect the three bones that make up the knee, but also keep the moving parts both flexible and stable. The ligaments limit rotation and sideways motion, which could cause injury to the knee, and yet allow the joint to flex and extend within a precisely calibrated range of motion.

It’s when the knee joint is stressed beyond what the ligaments can bear that injuries occur. This includes in a fall, during a jump, from a collision or in the unexpected shift of weight that occurred when you stepped into that hole. In the case of hyperextension, the resulting injury is typically to the anterior cruciate ligament, or ACL, and the posterior cruciate ligament, or PCL, which run through the center of the knee.

When someone hyperextends their knee, they usually feel the joint move out of alignment with the leg, just as you did. It often results in localized pain that ranges from moderate to severe. You may see swelling or even visible bruising in the area. Straightening the joint may cause pain, and the knee may feel weak or unstable.

When someone experiences a loss of mobility in the knee following hyperextension, it can be a sign of damage to the ligaments, and perhaps to the surrounding tissue. Depending on how severe the injury is, treatment can range from rest, the use of a knee brace for stability and over-the-counter meds for pain and inflammation to surgical repair and physical therapy. In mild injuries, recovery time can take from two to four weeks. When surgery is required, full recovery can take up to six months or more.

Because the knee is such an important and complex joint, we think it’s a good idea to have your injury assessed by your doctor.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)