Could sarcoidosis affect platelet levels?

Q. Is there a link between sarcoidosis and idiopathic thrombocytopenic purpura? I was diagnosed two years ago with sarcoidosis and am now battling idiopathic thrombocytopenic purpura.

A. Sarcoidosis is a condition in which there is inflammation in one or more parts of the body. The lung is most commonly affected, but skin, lymph nodes, and eyes are also common sites. Symptoms depend on which parts of the body are affected. Common symptoms include cough, shortness of breath, eye pain, and rash. However, sarcoidosis often causes no symptoms. Although its cause is unknown, sarcoidosis is thought to be autoimmune — that is, it develops due to a misguided attack by the immune system on healthy tissue.

Immune thrombocytopenic purpura (ITP) is a disease in which there are too few platelets, the blood cells that form clots and prevent bleeding after a cut or other injury. The name stands for

• immune (referring to the body’s immune system, which normally acts to defend the body from infection, toxins, and other threats)
• thrombocytopenic (the medical term for low platelets)
• purpura (purple spots in the skin that often develop in people with thrombocytopenia).

People with ITP may have no symptoms, or they may have abnormal bleeding or bruising throughout the body. Like sarcoidosis, ITP is an autoimmune disease in which the immune system turns on its owner.

When treatment is necessary, corticosteroids are usually the first choice for both conditions.

If steroids are not promptly effective for sarcoidosis, or if treatment causes intolerable side effects, other suppressors of the immune system, such as methotrexate or azathioprine, may be recommended.

For ITP, initial treatment may include steroids or injections of a protein (called gamma globulin) collected from blood donors. Other options include romiplostim, which can boost platelet production, or tranexamic acid, which stabilizes blood clots to reduce bleeding. If these measures are not promptly effective, surgery to remove the spleen may be recommended.

Sarcoidosis may lead to ITP by causing hypersplenism (enlargement and hyperactivity of the spleen), invasion of the bone marrow, or by causing production of abnormal antibodies that destroy platelets. It's also important to consider medications as a cause of low platelets: if a medicine used to treat sarcoidosis, such as methotrexate, causes low platelets, a change of medications may return the platelet count to normal.

Several studies have reported the simultaneous occurrence of sarcoidosis and ITP, raising the possibility that they are truly linked rather than occurring together just by chance. The earliest report I could find describing both conditions in a single person was published in 1938. Since then, only a small number of similar cases have been reported.

The true nature of the connection between ITP and sarcoidosis remains uncertain. Similarly, it is unknown exactly how often they occur together.

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