All Diseases

Approximately 15 percent of couples are infertile. This means they aren't able to conceive a child even though they've had frequent, unprotected sexual intercourse for a year or longer. In about half of these couples, male infertility plays a role.

Male infertility is due to low sperm production, abnormal sperm function or blockages that prevent the delivery of sperm. Illnesses, injuries, chronic health problems, lifestyle choices and other factors can play a role in causing male infertility.

Not being able to conceive a child can be stressful and frustrating, but a number of male infertility treatments are available.

Mammary duct ectasia (ek-TAY-zhuh) occurs when a milk duct beneath your nipple becomes wider (dilated), the duct walls thicken and the duct fills with fluid. The milk duct can then become blocked or clogged with a thick, sticky substance. The condition often causes no symptoms, but some women may have nipple discharge, breast tenderness or inflammation of the clogged duct (periductal mastitis).

Your chance of developing mammary duct ectasia — with or without inflammation — increases with age. Mammary duct ectasia usually improves without treatment. However, if symptoms persist despite self-care measures, you may need antibiotics or possibly surgery to remove the affected milk duct.

Though it's normal to worry about any changes in your breasts, mammary duct ectasia and periductal mastisis aren't risk factors for breast cancer.

Marfan syndrome is an inherited disorder that affects connective tissue — the fibers that support and anchor your organs and other structures in your body. Marfan syndrome most commonly affects the heart, eyes, blood vessels and skeleton.

People with Marfan syndrome are usually tall and thin with disproportionately long arms, legs, fingers and toes. The damage caused by Marfan syndrome can be mild or severe. If your heart or blood vessels are affected, the condition can become life-threatening.

Treatment usually includes medications to keep your blood pressure low to reduce the strain on weakened blood vessels. Depending on the severity of your symptoms and the part of your body that's affected, surgery may be necessary.

Mastitis is an infection of the breast tissue that results in breast pain, swelling, warmth and redness of the breast. If you have mastitis, you might also experience fever and chills. Mastitis most commonly affects women who are breast-feeding (lactation mastitis), although sometimes this condition can occur in women who aren't breast-feeding.

In most cases, lactation mastitis occurs within the first three months after giving birth (postpartum), but it can happen later during breast-feeding. The condition can leave you feeling exhausted and run-down, making it difficult to care for your baby.

Sometimes mastitis leads a mother to wean her baby before she intends to. But you can continue breast-feeding while you have mastitis.

Measles is a childhood infection caused by a virus. Once quite common, measles can now almost always be prevented with a vaccine. Signs and symptoms of measles include cough, runny nose, inflamed eyes, sore throat, fever and a red, blotchy skin rash.

Also called rubeola, measles can be serious and even fatal for small children. While death rates have been falling worldwide as more children receive the measles vaccine, the disease still kills more than 100,000 people a year, most under the age of 5.

As a result of high vaccination rates, measles has not been widespread in the United States for more than a decade. Today, the United States averages about 60 cases of measles a year, and most of them originate outside the country.

Melanoma, the most serious type of skin cancer, develops in the cells (melanocytes) that produce melanin the pigment that gives your skin its color. Melanoma can also form in your eyes and, rarely, in internal organs, such as your intestines.

The exact cause of all melanomas isn't clear, but exposure to ultraviolet (UV) radiation from sunlight or tanning lamps and beds increases your risk of developing melanoma. Limiting your exposure to UV radiation can help reduce your risk of melanoma.

The risk of melanoma seems to be increasing in people under 40, especially women. Knowing the warning signs of skin cancer can help ensure that cancerous changes are detected and treated before the cancer has spread. Melanoma can be treated successfully if it is detected early.

Membranous nephropathy (MEM-bruh-nus nuh-FROP-uh-thee) occurs when the small blood vessels in the kidney (glomeruli), which filter wastes from the blood, become inflamed and thickened. As a result, proteins leak from the damaged blood vessels into the urine (proteinuria). For many, loss of these proteins eventually causes signs and symptoms known as nephrotic syndrome.

In mild cases, membranous nephropathy may get better on its own, without any treatment. As protein leakage increases, so does the risk of long-term kidney damage. In many, the disease ultimately leads to kidney failure. There's no absolute cure for membranous nephropathy, but successful treatment can lead to remission of proteinuria and a good long-term outlook.

Meniere's disease is a disorder of the inner ear that causes spontaneous episodes of vertigo — a sensation of a spinning motion — along with fluctuating hearing loss, ringing in the ear (tinnitus), and sometimes a feeling of fullness or pressure in your ear. In many cases, Meniere's disease affects only one ear.

People in their 40s and 50s are more likely than people in other age groups to develop Meniere's disease, but it can occur in anyone, even children.

Although Meniere's disease is considered a chronic condition, various treatment strategies can help relieve symptoms and minimize the disease's long-term impact on your life.

A meningioma is a tumor that arises from the meninges — the membranes that surround your brain and spinal cord. Most meningiomas are noncancerous (benign), though rarely a meningioma may be cancerous (malignant). Some meningiomas are classified as atypical, meaning they're neither benign nor malignant but, rather, something in between.

Meningiomas occur most commonly in older women. But a meningioma can occur in males and at any age, including childhood.

A meningioma doesn't always require immediate treatment. A meningioma that causes no significant signs and symptoms may be monitored over time.

Meningitis is an inflammation of the membranes (meninges) surrounding your brain and spinal cord.

The swelling associated with meningitis often triggers the "hallmark" signs and symptoms of this condition, including headache, fever and a stiff neck.

Most cases of meningitis in the U.S. are caused by a viral infection, but bacterial and fungal infections also can lead to meningitis. Depending on the cause of the infection, meningitis can get better on its own in a couple of weeks — or it can be a life-threatening emergency requiring urgent antibiotic treatment.

If you suspect that you or someone in your family has meningitis, seek medical care right away. Early treatment of bacterial meningitis can prevent serious complications.