All Diseases

Morphea (mor-FEE-uh) is a rare skin condition that causes reddish or purplish patches on your skin. Morphea is a localized or limited form of scleroderma, a condition that can cause a wide variety of problems, from skin discoloration to difficulty with the function of joints and muscles and other connective tissues.

Morphea typically appears on your abdomen, chest or back, but it can affect your face, arms and legs. Morphea tends to affect only the outermost layers of your skin — the dermis and the fatty tissue just beneath the dermis. Sometimes, morphea can restrict movement in your joints.

Morphea generally subsides on its own over time. With morphea, you may be concerned about your appearance. Your doctor may recommend medications and other treatments to help with your appearance and other symptoms of morphea.

Morton's neuroma is a painful condition that affects the ball of your foot, most commonly the area between your third and fourth toes. Morton's neuroma may feel as if you are standing on a pebble in your shoe or on a fold in your sock.

Morton's neuroma involves a thickening of the tissue around one of the nerves leading to your toes. This can cause a sharp, burning pain in the ball of your foot. Your toes also may sting, burn or feel numb.

High-heeled shoes have been linked to the development of Morton's neuroma. Many people experience relief by switching to lower heeled shoes with wider toe boxes. Sometimes corticosteroid injections or surgery may be necessary.

Mosquito bites are the itchy bumps that appear after mosquitos use their mouthparts to puncture your skin and feed on your blood. Most mosquito bites are harmless, but occasionally a mosquito bite causes a large area of swelling, soreness and redness. This type of reaction, most common in children, is sometimes referred to as skeeter syndrome.

Bites from mosquitoes carrying certain viruses or parasites can cause severe illness. Infected mosquitoes in many parts of the world transmit West Nile virus to humans. Other mosquito-borne infections include yellow fever, malaria and some types of brain infection (encephalitis).

Mouth cancer refers to cancer that develops in any of the parts that make up the mouth. Mouth cancer can occur on the:

  • Lips
  • Gums
  • Tongue
  • Inside lining of the cheeks
  • Roof of the mouth
  • Floor of the mouth

Cancer that occurs on the inside of the mouth is sometimes called oral cancer or oral cavity cancer.

Mouth cancer is one of several types of cancer grouped in a category called head and neck cancers. Mouth cancer and other head and neck cancers are often treated similarly.

Methicillin-resistant Staphylococcus aureus (MRSA) infection is caused by a strain of staph bacteria that's become resistant to the antibiotics commonly used to treat ordinary staph infections.

Most MRSA infections occur in people who've been in hospitals or other health care settings, such as nursing homes and dialysis centers. When it occurs in these settings, it's known as health care-associated MRSA (HA-MRSA). HA-MRSA infections typically are associated with invasive procedures or devices, such as surgeries, intravenous tubing or artificial joints.

Another type of MRSA infection has occurred in the wider community — among healthy people. This form, community-associated MRSA (CA-MRSA), often begins as a painful skin boil. It's spread by skin-to-skin contact. At-risk populations include groups such as high school wrestlers, child care workers and people who live in crowded conditions.

Multiple myeloma is a cancer that forms in a type of white blood cell called a plasma cell. Plasma cells help you fight infections by making antibodies that recognize and attack germs.

Multiple myeloma causes cancer cells to accumulate in the bone marrow, where they crowd out healthy blood cells. Rather than produce helpful antibodies, the cancer cells produce abnormal proteins that can cause kidney problems.

Treatment for multiple myeloma isn't always necessary. If you're not experiencing signs and symptoms, you may not require treatment. If signs and symptoms develop, a number of treatments can help control your multiple myeloma.

Multiple sclerosis (MS) is a disease in which your immune system attacks the protective sheath (myelin) that covers your nerves. Myelin damage disrupts communication between your brain and the rest of your body. Ultimately, the nerves themselves may deteriorate, a process that's currently irreversible.

Signs and symptoms vary widely, depending on the amount of damage and which nerves are affected. Some people with severe MS may lose the ability to walk independently or at all, while others experience long periods of remission during which they develop no new symptoms.

There's no cure for multiple sclerosis. However, treatments can help speed recovery from attacks, modify the course of the disease and manage symptoms.

Multiple system atrophy (MSA) is a rare neurological disorder that impairs your body's involuntary (autonomic) functions, including blood pressure, heart rate, bladder function and digestion.

Formerly called Shy-Drager syndrome, the condition shares many Parkinson's disease-like symptoms, such as slowness of movement, muscle rigidity and poor balance.

Multiple system atrophy is a degenerative disease that develops in adulthood, usually in the 50s or 60s.

Treatment for MSA includes medications and lifestyle changes to help manage symptoms. The condition progresses gradually and eventually leads to death.

Mumps is a viral infection that primarily affects the parotid glands — one of three pairs of saliva-producing (salivary) glands, situated below and in front of your ears. If you or your child contracts mumps, it can cause swelling in one or both parotid glands.

Mumps was common in the United States until mumps vaccination became routine. Since then, the number of cases has dropped dramatically, so your odds of getting mumps are low. Complications of mumps, such as hearing loss, are potentially serious, but rare.

There's no specific treatment for mumps. Mumps outbreaks still occur in the United States, and mumps is still common in many parts of the world, so getting a vaccination to prevent mumps remains important.

A muscle cramp is a sudden and involuntary contraction of one or more of your muscles. If you've ever been awakened in the night or stopped in your tracks by a sudden charley horse, you know that muscle cramps can cause excruciating pain. Though generally harmless, muscle cramps can make it temporarily impossible to use the affected muscle.

Long periods of exercise or physical labor, particularly in hot weather, may lead to muscle cramps. Some medications and certain medical conditions also may cause muscle cramps. You can usually treat muscle cramps at home with self-care measures.