Tuberculosis (TB) is a serious infection that usually affects only your lungs, which is why it’s often called pulmonary tuberculosis. However, sometimes the bacteria get into your blood, spread throughout your body, and grow in one or several organs. This is called miliary TB, a disseminated form of tuberculosis.
Miliary TB got its name in 1700 from John Jacob Manget based on how it appears on autopsy findings, after a patient had died. The bodies would have a lot of very small spots similar to hundreds of tiny seeds about 2 millimeters long scatted in various tissues. Since a millet seed is about that size, the condition became known as miliary TB. It’s a very serious, life-threatening illness.
This condition is rare in people with a normal immune system. It’s more common in people whose immune system isn’t working right. This is called being immunocompromised.
Often your lungs, bone marrow, and liver are affected in miliary TB, but it can also spread to the lining of your heart, your spinal cord and brain, and other parts of your body. According to the Centers for Disease Control and Prevention, the lining of the brain is infected in 25 percent of people who have miliary TB. It’s important to look for this because it requires longer treatment.
TB is caused by bacteria called Mycobacterium tuberculosis. It’s contagious and is transmitted when someone with an active TB infection in their lung releases the bacteria into the air by coughing or sneezing, and someone else inhales it. It can stay airborne for a few hours.
When you have the bacteria in your body but your immune system is strong enough to fight it, it’s called latent TB. With latent TB, you don’t have symptoms and aren’t contagious. If your immune system stops working properly, latent TB can turn into active TB. You’ll have symptoms and be contagious.
Until the 1980s, miliary TB was seen mainly in infants and children. Now it’s found a lot more often in adults. This is because becoming immunocompromised is much more common today.
Anything that weakens your immune system increases your risk of getting any kind of TB. Miliary TB usually occurs only if your immune system is very weak. Conditions and procedures that can weaken your immune system include:
- HIV and AIDS
- chronic kidney disease
- cancer in your lung, neck, or head
- being pregnant or recently giving birth
- long-term dialysis
Those who are on medications that work by changing or turning down the immune system are also at greater risk for miliary TB. The most common is long-term corticosteroid use, but drugs that are used after an organ transplant or to treat immune diseases and cancer can also weaken your immune system and increase your risk of miliary TB.
The symptoms of miliary TB are very general. They can include:
- a fever that goes on for several weeks and may be worse in the evening
- dry cough that may occasionally be bloody
- shortness of breath that increases with time
- poor appetite
- weight loss
- night sweats
- just not feeling well in general
If other organs besides your lungs are infected, these organs may stop working properly. This can cause other symptoms, such as low levels of red blood cells if your bone marrow is affected or a characteristic rash if your skin is involved.
The symptoms of miliary TB are the same as those in many illnesses, and the bacteria can be hard to find when your blood, other fluids, or tissue samples are looked at under a microscope. This makes it hard for your doctor to diagnose and differentiate from other possible causes of your symptoms. Several different tests may be needed for your doctor to make the diagnosis.
A tuberculin skin test called a PPD test shows if you've ever been exposed to the bacteria that causes TB. This test can’t tell you if you currently have an active infection; it only shows if you’ve been infected at some point. When you’re immunocompromised, this test may indicate you don’t have the disease even when you do.
Your doctor will order a chest X-ray if your skin test is positive or if you have symptoms that suggest TB. Unlike typical TB that can look like other infections, the millet seed pattern on a chest X-ray is very characteristic of miliary TB. When the pattern is seen, it’s easier to make the diagnosis, but sometimes it doesn’t show up until you’ve had the infection and symptoms for a long time.
Other tests that your doctor may order to confirm the diagnosis of miliary TB are:
- a CT scan, which gives a better image of your lungs
- sputum samples to look for the bacteria under a microscope
- a blood test that can detect exposure to the bacteria
- a bronchoscopy in which a thin, lighted camera is inserted through your mouth or nose into your lungs so your doctor can look for abnormal spots and get samples to look at under a microscope
Since miliary TB affects organs in your body besides your lungs, your doctor may want other tests depending on where they think the infection is:
- a CT scan of other parts of your body, especially your abdomen
- an MRI to look for infection in your brain or spinal cord
- an echocardiogram to look for an infection and fluid in the lining of your heart
- a urine sample to look for bacteria
- a bone marrow biopsy, where a needled is inserted into the middle of a bone to take a sample to look for bacteria under a microscope
- a biopsy, in which a small piece of tissue is taken from an organ thought to be infected and looked at with a microscope to find the bacteria
- a spinal tap if your doctor thinks the fluid around your spinal cord and brain is infected
- a procedure where a needle is inserted into a fluid collection around your lung to look for bacteria
Treatment is the same as for typical TB and may consist of:
You’ll be treated with several antibiotics for 6 to 9 months. Once the bacteria have been grown in a culture (which takes a long time), a lab will test to see if the usual antibiotics kill the strain of bacteria you have. Infrequently, one or more of the antibiotics won’t work, which is called drug resistance. If this happens, the antibiotics will be changed to some that work.
If the lining of your brain is infected, you’ll need 9 to 12 months of treatment.
Common antibiotics are:
You might be given steroids if the lining of your brain or heart are infected.
Rarely, you might develop complications, such as an abscess, that require surgery to treat.
Miliary TB is a rare but contagious and life-threatening infection. Treating the illness requires more than a month of multiple antibiotics. It’s important that this infection is diagnosed as early as possible and that you take the antibiotics for as long as directed. This allows for a good outcome and stops the possibility of spreading it to other people. If you have any symptoms of TB, or know of recent exposure to the disease, contact your doctor’s office for an appointment as soon as possible.