Misdiagnosed: 10 diseases doctors often get wrong

When you experience strange pains, mysterious indigestion, or other seemingly disconnected symptoms, your first hope is that a trip to the doctor will solve your health woes. However, doctors are human, and humans make mistakes.

"A lot of symptoms are nonspecific and variable, depending on the person," says Dr. David Fleming, president of the American College of Physicians and a professor of medicine at the University of Missouri. "On top of that, many diagnostic tests are expensive and aren't done routinely, and even then they don't always give us a black and white answer."

The following 10 conditions are notoriously difficult to pin down according to Health.com.

1. Irritable bowel syndrome (IBS)

Some conditions, like IBS, don’t have any sort of real test to prove their existence; rather, they require a "diagnosis of elimination," says Fleming, as doctors rule out all other possibilities. IBS is a chronic condition that affects the large intestine and causes abdominal pain, cramping, bloating, diarrhea, and/or constipation. According to diagnostic criteria, IBS can’t be taken into consideration unless symptoms persist for at least six months. Discomfort should typically be present at least three days a month before being diagnosed with IBS.

2. Celiac disease

There is a lot of confusion around celiac disease -- an immune reaction to gluten that triggers inflammation in the small intestine. It can take an average patient 6 to 10 years to be properly diagnosed. Those with celiac would have digestive problems when eating gluten-containing foods like diarrhea, cramping indigestion, weight loss, itchy skin, headaches, joint pain, and acid reflux or heartburn. All of the above symptoms can also be attributed to something else. The good news: a blood test can diagnose celiac disease regardless of what symptoms are present, and an endoscopy can determine any damage that's been done to the small intestine.

3. Fibromyalgia

Fibromyalgia, characterized by widespread musculoskeletal pain, involves "medically unexplained symptoms" -- a term doctors use to describe persistent complaints that don't appear to have an obvious cause. When doctors can't find a root cause for a patient's chronic pain and fatigue, they often end on this diagnosis. This may involve seeing a variety of specialists to rule out other diseases, says Dr. Eugene Shapiro, deputy director of the Investigative Medicine Program at Yale University. "There are studies that show that people with certain symptoms who show up at a rheumatologist will be diagnosed with fibromyalgia, but if the same patients show up at a gastroenterologist they'll be diagnosed as having irritable bowel syndrome."

4. Multiple sclerosis (MS)

This autoimmune disease occurs when the immune system attacks the body's own nerve cells and disrupts communication between the brain and the rest of the body. Some of the first symptoms of MS are often numbness, weakness, or tingling in one or more extremity, but that's not always the case.

"Multiple sclerosis can be episodic; the disease waxes and wanes," says Shapiro.

Depending on the number and location of lesions in the brain, signs and symptoms may be more or less severe. Once a doctor does suspect MS, however, a sample of spinal fluid or MRI imaging can help confirm the diagnosis.

5. Endometriosis

Like appendicitis, vague stomach pain can go unnoticed. However, women with endometriosis (in which uterine tissue grows outside the uterus) often report pelvic pain, cramping, and heavy bleeding that are far worse than usual. A red flag: this bleeding gets worse over time. A pelvic exam can sometimes detect endometrial tissue or cysts that have been caused by it. In other cases, an ultrasound or laparoscopy is required for a definite diagnosis.

6. Appendicitis

Typical appendicitis symptoms include nausea, pain and tenderness in the abdomen, and possibly a low-grade fever. These symptoms are vague, and especially easily to go ignored in females.

"Some people have an appendix that points backward instead of forward in the body, so the symptoms present in a different location," says Shapiro. "And sometimes people do have pain, but then the appendix ruptures and the pain is relieved so they think they're fine." In this case, he says, intestinal fluids can leak into the entire abdomen and cause a potentially life-threatening infection -- but it can take days or even weeks before these symptoms appear.

7. Lyme disease

You probably know to look out for tick bites and the characteristic rash that can form if a person is infected with Lyme disease. However, not everyone develops this rash and tick bites can be hard to spot. Lyme disease's other symptoms of fatigue, headaches, joint pain, and flu-like symptoms can also easily be confused for other conditions.

A blood test can check for Lyme disease, but the test usually doesn’t show positive until a few weeks after infection when more antibodies are present in the blood. If you do find a tick and/or tick bite on yourself or a loved on, it's important to remove the tick immediately and see a doctor right away. Quickly removing a tick can possibly prevent the transfer of dangerous bacteria. Moreover, antibiotics for Lyme disease are most effective when given immediately.

8. Inflammatory bowel disease (IBD)

There are primarily two types of IBD: Crohn's disease and ulcerative colitis. Both cause inflammation of the digestive tract, as well as pain, diarrhea, and possibly even malnutrition. There's no one test for IBD, and again it can appear as vague stomach pain.

"If a patient comes in with severe abdominal pain, we might first think it's their gallbladder," says Shapiro. "If he comes in with loose stools, we might think it's an infection. So we go through a litany of tests -- imaging, blood tests, assessments -- and sometimes we finally come down to the fact that we've ruled out every other possibility, so this is what we're going to treat you for and we'll see if it works."

9. Cluster headaches

A rare headache disorder that's often extremely painful and extremely misunderstood—cluster headaches currently affect less than 1 million Americans. Cluster headaches tend to occur close together and last on average 30 minutes to three hours. Scientists aren't sure why, but cluster headaches tend to occur when seasons change or during periods of high stress.

10. Diabetes

Unlike Type 1 diabetes, Type 2 diabetes may be diagnosed later in life. If left untreated, it can cause life-threatening damage to major organs. Before signs of diabetes develop, says Fleming, adults can have diabetes for years without knowing it.

"There are a lot of people out there with elevated blood sugar levels who aren't getting to the doctor regularly, so they aren't getting checked for it," he says. "They won't realize it until it gets severe enough that they start developing side effects, like problems with their vision or numbness in their feet or hands."

Watch for earlier symptoms like increased thirst, frequent urination (particularly at odd hours of the night), sudden weight loss, and fatigue.