Whether you’ve just been diagnosed with ITP or have been living with low platelet counts for some time, you may wonder if the condition was inherited through your family—and if there’s a chance you’ll pass on ITP to future generations.
There are two distinct types of immune thrombocytopenia (ITP): primary and secondary. Primary ITP is when an individual has a diagnosis of immune thrombocytopenia (low platelet count due to an immune cause) in absence of any identifiable immune disorder. Secondary ITP is when a low platelet count is due to an underlying immune disorder. This may be an underlying viral infection, rheumatologic disorder such as lupus or rheumatoid arthritis, primary bone marrow disorder such as chronic lymphocytic leukemia, or an underlying immune disease such as common variable immune deficiency. It is not uncommon for individuals with ITP to have a diagnosis of primary ITP for years before they learn their low platelet count is ‘secondary’ to something else. In fact, 1 in 7 adults with ITP are misdiagnosed as having primary ITP when their low platelet count and bleeding symptoms are due to a different condition (Arnold et al., 2017). This is often because there is no reliable way early on to determine who has secondary ITP.
Inherited platelet disorders (IPDs) are another known cause for a low platelet count. IPDs are not considered to be primary or secondary ITP but rather ‘genetic’ conditions.
IPDs or “congenital platelet disorders” may be present at birth or early in childhood and may be associated with other medical problems. Some inherited platelet disorders are quite complex and affect many parts of the body while others are very limited to affecting only the platelets. It is not uncommon for patients to be diagnosed initially with ITP, and later learn they have an IPD, sometimes years after the initial ITP diagnosis.
Your hematologist should think about secondary ITP and IPDs when the following risk factors are present:
- Family history of thrombocytopenia, anemia (low red blood cell count), leukopenia (low white blood cell count), and/or blood cancers
- Enlarged liver and/or spleen or lymph nodes
- Resistance to standard ITP therapies (corticosteroids, IVIG and/or TPO-RA)
- Unexpected bleeding for degree of thrombocytopenia
- Abnormalities in platelet size or shape
- Low platelet counts that have been present since birth or early in childhood
Additional clues that you may have an inherited platelet disorder include:
- Bleeding out of proportion to the platelet count
- Strong family history of low platelet counts or blood cancers
- Additional abnormalities present since birth (congenital heart disease, skeletal abnormalities)
- Thrombocytopenia from birth or early childhood
- Lack of response to splenectomy
- Family history (or personal history) of hearing loss, cataracts, liver disease or kidney disease