Properly diagnosing medical conditions is not as easy and straightforward as it seems. Many medical conditions share common symptoms and lack specific tests, so misdiagnosis is more common than you may think. That’s why it’s important to ask your doctor follow-up questions and, in some cases, seek a second opinion. For a variety of reasons, these four specific conditions are commonly prone to medical misdiagnosis. 1. Polycystic Ovary Syndrome Polycystic ovary syndrome (PCOS) is a medical condition characterized by ovarian cysts and increased production of male hormones in female patients. PCOS can cause irregular menstrual periods, infertility, pelvic pain, facial hair, weight gain, acne and thickened skin. Because the symptoms affect so many different systems of the body, and can vary over time (and from woman to woman), it can be difficult to diagnose. Many women with PCOS say it took years to receive an accurate diagnosis. Such a delay is troubling, because untreated PCOS increases a woman’s risk of diabetes, metabolic syndrome, heart disease, and high blood pressure. If you have any of the symptoms of PCOS and your doctor brushes off your concerns or orders a treatment that doesn’t improve your symptoms, seek a second opinion. 2. Lupus Lupus is a chronic autoimmune disease that causes inflammation throughout the body and can affect the joints, skin, kidneys, heart, lungs, blood vessels, and brain. The textbook symptom of lupus is a butterfly-shaped rash on the face, but this rash doesn’t appear in all cases. Symptoms vary from person to person and may include joint or muscle pain, fever, hair loss, chest pain during deep breaths, sun sensitivity, pale or purplish fingers or toes, mouth ulcers, swollen glands, fatigue, and swelling of the legs or around the eyes. Depending on which symptoms are present, it’s easy to see how lupus might be misdiagnosed. A person whose primary symptom is swollen or sore joints, for instance, might be diagnosed with rheumatoid arthritis. Some people with lupus are misdiagnosed with chronic fatigue syndrome or fibromyalgia, and many go years without a proper diagnosis. You can help your doctor arrive at a proper diagnosis by discussing your symptoms honestly and in detail. If your symptoms continue after your doctor’s initial diagnosis, don’t be afraid to go back for another appointment or to see another doctor for a second opinion. 3. Parkinson’s Disease Approximately 25% of Parkinson’s disease diagnoses are wrong, according to the Michael J. Fox Foundation for Parkinson’s Research. Some of the characteristic symptoms of Parkinson’s disease—poor balance, difficulty walking, and hand tremors—are also symptoms of other medical conditions, including essential tremor, progressive supranuclear palsy, and normal pressure hydrocephalus. Certain medications also cause side effects that mimic Parkinson’s disease. And sometimes, Parkinson’s symptoms are mistakenly attributed to stress, stroke, or traumatic head injury. Because of the difficulty involved in accurately diagnosing Parkinson’s disease, the Michael J. Fox Foundation recommends that anyone who experiences Parkinson’s symptoms consult with a movement disorders specialist. 4. Lyme Disease Lyme disease is a bacterial infection humans can contract after being bitten by infected ticks. Many people are familiar with Lyme disease’s so-called “bulls-eye rash,” but the rash doesn’t occur in everyone who has Lyme disease. Other Lyme disease symptoms–fatigue, headaches, body aches, joint pain and fever–are so commonplace that many people write them off altogether, or mistakenly attribute them to the flu. People who seek medical attention for Lyme disease symptoms are sometimes misdiagnosed with mononucleosis, chronic fatigue syndrome, fibromyalgia, or meningitis. A blood test can be used to detect Lyme disease, but it can’t catch the disease in the first few weeks after infection. If Lyme disease symptoms continue for a period of weeks, ask your doctor to perform the blood test, especially if you live in or have recently spent time in an area where ticks are present. Bottom line: If you feel uneasy about your diagnosis, listen to your gut. Consider getting a second opinion; most doctors are happy to provide recommendations—especially with challenging diagnostic dilemmas. You’ll feel better if the second opinion confirms the first diagnosis–and if it doesn’t, you’ll be one step closer to an appropriate diagnosis and treatment.