A tapeworm is a flat, parasitic worm that lives in the intestines of an animal host. It commonly infects many different animals, including humans, livestock and domestic cats and dogs (usually meat-eating mammals.) Like other parasites, the mature tapeworm can only survive inside the host animal, feeding off of the host’s own nutrients. The head attaches to the inside of your intestines …

When you have tachycardia, your heart beats faster than normal for a few seconds to a few hours. Normally, your heart rate is 60 to 100 beats per minute when you’re not active. When your heart beats more than 100 times a minute at rest, that’s tachycardia. Because your heart beats too often, it doesn’t have the time it needs …

“Lymphoma” is the general term for cancer in your lymphatic system — the network of tissues, vessels and organs that help your body fight infection. It’s considered a blood cancer because the condition starts in white blood cells (lymphocytes) in your lymphatic system. There are two main lymphoma categories — Hodgkin lymphoma and non-Hodgkin lymphoma — and more than 70 lymphoma subtypes. Lymphomas can be aggressive (fast-growing) or …

Lymphedema is swelling in various areas of your body that happens when something affects your lymphatic system. Your lymphatic system collects excess fluid, proteins and toxins from your cells and tissues and returns them to your bloodstream. When your lymphatic system doesn’t work well, your body accumulates fluid and may begin to swell. The swelling typically affects your arms and legs, …

Swollen lymph nodes usually occur as a result of infection from bacteria or viruses. Rarely, swollen lymph nodes are caused by cancer. Your lymph nodes, also called lymph glands, play a vital role in your body’s ability to fight off infections. They function as filters, trapping viruses, bacteria and other causes of illnesses before they can infect other parts of …

Lyme disease is caused by a bacteria, Borrelia burgdorferi, which you can get if an infected deer tick (also called black-legged tick) bites you. Ordinary “wood ticks” and “dog ticks” don’t carry the infection. The first recognition of Lyme disease, also called borreliosis, began in 1975 when many children received a diagnosis of juvenile rheumatoid arthritis in Lyme, Connecticut, and two neighboring towns. …

Lupus nephritis is inflammation and damage in your kidneys due to systemic lupus erythematosus (SLE). SLE is the most common form of lupus. Lupus is an autoimmune disease that triggers your immune system to attack your tissues. In addition to your kidneys, lupus can damage your brain, heart, joints, skin and other parts of your body. Lupus nephritis prevents your kidneys from: Controlling …

Lupus is a condition that causes inflammation throughout your body. It’s an autoimmune disease, which means your immune system damages your body instead of protecting it. You may experience symptoms throughout your body depending on where your autoimmune system damages tissue, including in your: Skin. Blood. Joints. Kidneys. Brain. Heart. Lungs. Visit a healthcare provider if you notice new pain, rashes or changes …

Low testosterone (male hypogonadism) is a condition in which your testicles don’t produce enough testosterone (the male sex hormone). Testicles are the gonads (sex organs) in people assigned male at birth (AMAB). More specifically, the Leydig cells in your testicles make testosterone. Low testosterone causes different symptoms at different ages. Testosterone levels in adults AMAB naturally decline as they age. This includes cisgender …

Oligospermia is a term that means you have a low sperm count. One medical definition is that you have fewer than 15 million sperm in 1 milliliter of semen. A typical sperm count is more than 15 million sperm per 1 milliliter of semen. Besides being known as low sperm count, oligospermia is also called oligozoospermia. A severely low sperm …