Back in the 1960s, scientists in Texas started studying cells from a kid in Chicago who was afflicted with a rare disease that caused his cholesterol to be 6 times higher than a normal person's.

He had a disease called familial hypercholesterolemia, a rare metabolic disorder that causes high levels of cholesterol in the blood, artery-clogging plaques, and heart attacks as early as age 35.

Biochemists Michael Brown and Joseph Goldstein learned a lot from the patient's cells and their work eventually earned them a Nobel Prize. It led to the development of statins, a cholesterol-lowering drug, and a new way of treating heart disease.

"Their study of a rare disease revolutionized how we treat one of the most common diseases and the #1 cause of death in the world," says Dr. Tyler Pierson, a pediatric neurologist and rare disease expert.

More than 7,000 rare diseases (conditions that affect fewer than 200,000 people) have been identified by scientists and doctors.

Some of them might only affect a handful of people while others might affect thousands. Treating and studying these diseases help those living with them—and frequently offers important insights into how to treat more common diseases.

In Discoveries: Recipe for Disaster

As many as 30 million Americans have been diagnosed with a rare disease (defined as a condition that affects fewer than 200,000 people), according to the National Institutes of Health.

About 80% of rare diseases are inherited and the majority of people with these conditions are children. Most are due to rare genetic disorders that can cause a collection of seemingly unconnected symptoms.

Dr. Pierson sees these cases in the Pediatric Neurogenetics and Neuromuscular program, as well as in his role as the pediatric lead for the Center for the Undiagnosed Patient.

We asked Cedars-Sinai experts to share some facts about rare diseases they've treated or are often asked about.

Batten disease
What is it? Batten disease is a group of disorders caused by genetic mutations that disrupt the cells' ability to dispose of wastes. Proteins and fats then build up in the cells and throw them off balance. The resulting cell damage causes neurological impairment that becomes worse over time. The symptoms vary from person to person and frequently include seizures, visual impairment, personality and behavior changes, muscle weakness, and cognitive problems. There are 14 known forms of the disease.

How many people does it affect? 2-4 children per 100,000 births in the US.

What's on the horizon? "Here at Cedars-Sinai, we're studying specific types of this disease," Dr. Pierson says. "Paying attention to these diseases and doing good research benefits everyone."

Alpha-1 antitrypsin deficiency
What is it? Alpha-1 antitrypsin deficiency (AATD) a is a genetic condition that may cause lung and liver disease. People with this condition don't produce enough of an enzyme that helps protect organs from damage, says Dr. Jeremy Falk, associate director of the Lung Transplant program. The usual treatment is weekly IV infusions of the missing enzyme.

How many people does it affect? There are at least 100,000 people in the US with the disease. The gene mutation itself is more common. About 2% of people are carriers for the disease, but not everyone develops problems. "It's one of those things where having the genetic predisposition isn't the same thing as having the disease," Dr. Falk says. "More than half of my patients are healthy, normal people."

For those who are carriers but who haven't developed the disease, their treatment is to manage their risk by taking good care of their lungs: Avoid smoking, avoid highly polluted areas, and get a flu shot every year.

What's on the horizon? Here are a couple of exciting developments being studied: Synthetic enzyme replacement could provide a plentiful and cost-effective alternative to the current treatment, which relies on donated blood. Second, some trials are looking at a medication that can be inhaled rather than given with an IV, which would be a big quality-of-life improvement.

Achalasia
What is it? Achalasia is a disorder that affects the esophagus, the tube that carries food from the mouth to the stomach. The muscle contractions are weak, and the entrance to the stomach gets narrow and tight. Over time, food and liquid get stuck in the esophagus, making it difficult to eat, says Dr. Harmik Soukiasian.

How many people does it affect? About 1 in 100,000 people in the US has achalasia.

What do you wish more people knew? The disease is treatable. Medications and several surgical interventions are available. Sometimes, the condition can be treated with Botox injections, which paralyze the nerves causing muscle contraction that blocks the esophagus. Surgery is also successful in up to 90% of people. "People with this disease can't eat," Dr. Soukiasian says. "We have treatments that are very successful and it completely changes people's lives."

In Discoveries: 3D Cameras Could Help Diagnose Rare Genetic Diseases

One of the problems facing families with a loved one who has a rare disease is finding a community to support them. This is one of the times that online resources and social media communities are especially helpful.

"You might be dealing with a disorder that has been reported in only a handful of families around the world," Dr. Pierson says. "Finding support can be as simple as typing the gene mutation into a Facebook search and finding a family group."

Another kind of networking is also aiding families: Groups of doctors and researchers from around the world frequently collaborate on rare disease research.

"You might have one patient in LA, another in Israel, and one in Scandinavia, and all the doctors can connect quickly to determine if they all have the same rare disorders," he says.