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What is sickle cell disease and how does MRI help to locate it

Sickle cells disease is an inherited group of red blood cell disorders, which manifest with an abnormal protein in the patient's red blood cells. Roughly 100,000 Americans were living with sickle cell disease in 2016.1 It is most common in people of African descent but can be common among those who are Hispanic. The disease can cause a variety of issues that affect different areas of the body, including the spleen, brain, lungs and more.

What is sickle cell disease?

Sickle cell disease, sometimes referred to as sickle cell anemia, is inherited from both parents.1,2,3 This means that patients with SCD are born with two sickle cell genes. If someone has only one sickle cell gene, they have sickle cell trait. Those who have sickle cell trait are typically healthy, but they are a carrier for the disease, which means that they can pass it to their children.

Babies with SCD typically begin to show signs of the disease at around 5 months of age.1,2,3 These symptoms can include painful swelling of the hands and feet, fatigue and fussiness from anemia or a yellowish color of the skin (known as jaundice) or the white of the eyes (referred to as icterus). The effects and severity of the disease varies between people, and other symptoms include severe pain, organ damage and infections.

Blood tests can show if someone has the genes, and states may test newborns for it.1,2,3 This test allows the treatment to begin early, rather than waiting for the symptoms to appear. In some cases, doctors may be able to test for SDC before birth, using the amniotic fluid or tissue taken from the placenta.

Unfortunately, the only cure for sickle cell disease is a bone marrow or stem cell transplant.1,2,3 These transplants are usually only used in children with severe SCD, due to the risks and side effects associated with the procedure. Additionally, the donor's bone marrow must be a close match to the patient's in order for it to work. Siblings are usually the best option for donors. Other treatments, such as antibiotics, pain relievers, immunizations, SCD targeted medicines and blood transfusions can help to reduce symptoms and complications.

Complications of SCD can include infection, acute chest syndrome and stroke. Normal blood cells are round and move through small blood vessels to other areas of the body.1,2,3 The red blood cells of a patient with sickle cell disease are hard, sticky and C-shaped (resembling the shape of a sickle). When a patient with SCD's blood cells tries to move through small blood vessels, they may get stuck and clog the blood flow. The sickle cells also die early, causing a shortage of red blood cells.

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Magnetic resonance imaging of sickle cell disease

Magnetic resonance imaging (MRI) can be used to monitor the effects of sickle cell disease in a couple of different ways. Because SCD affects so much of the body, doctors may decide to image for complications, whether those complications have manifested as symptoms or not. As a result of SCD, patients may experience musculoskeletal and neurological complications.

In terms of musculoskeletal complications of SCD, there are multiple issues that commonly arise. These include bone marrow abnormalities and osteomyelitis. Many of these abnormalities may be noted on MRI.

Bone marrow abnormalities in patients with SCD occur as a result of reconversion of yellow marrow to red marrow, after the red bone marrow has been replaced by yellow as a part of the natural aging process.4 This is associated with softening of long bones, which can increase the risk of insufficiency fractures, and may be seen on T1- and T2-weighted imaging. The soft tissue has intermediate signal intensity. Another bone marrow abnormality, resulting in oedematous changes in the marrow, can appear as areas of increased signal on MRI.

Osteomyelitis is often initially investigated with plain films.4 However, the poor sensitivity and specificity on these plain films prompt further evaluation with MRI for evaluation. It allows for early detection of osseous changes and other soft tissue and joint findings. Osteomyelitis may show as decreased marrow signal on T1-weighted images, increased signal on T2-weighted images and enhancement on contrast-enhanced T1-weighted images. Both T1- and T2-weighted imaging are important for discriminating between osteomyelitis and bone infarction.

Neuroimaging of SCD may show any of the musculoskeletal conditions, as well as infarction and ischemia.5 Infarction can lead to stroke syndrome in children with SCD associated with intracranial vasculopathy. Ischemia may not be accompanied by symptoms that correlate with objective abnormalities. It can be stable or show deterioration and impairment of cognitive function. Ischemia may be detectable using diffusion-weighted imaging (DWI) in the acute stage. Perfusion MRI may also be used to monitor cerebral blood flow and volume.

Sickle cell disease affects a large number of people in the United States, as well as the rest of the world. As a result these patients may have musculoskeletal and neurological issues associated with the disease. MRI may help to monitor these disorders, and possibly help physicians understand the disease and treatment options.

References

1. "About Sickle Cell Disease." genome.gov. 9 May 2016. Web. 5 June 2019. <https://www.genome.gov/Genetic-Disorders/Sickle-Cell-Disease>.

2. "Sickle Cell Disease: Also called: Hemoglobin SS disease, Sickle cell anemia." MedlinePlus.gov. 7 June 2018. Web. 5 June 2019. <https://medlineplus.gov/sicklecelldisease.html>.

3. "What is Sickle Cell disease?" CDC.gov. Web. 5 June 2019. <https://www.cdc.gov/ncbddd/sicklecell/facts.html>.

4. Vijaya Kosaraju, et al. "Imaging of musculoskeletal manifestations in sickle cell disease patients." Br J Radiol. May 2017; 90(1073): 20160130. Web. 11 June 2019. doi: 10.1259/bjr.20160130.

5. S. C. Thust, C. Burke and A. Siddiqui. "Neuroimaging findings in sickle cell disease." Br J Radiol. August 2014; 87(1040): 20130699. Web. 11 June 2019. doi: 10.1259/bjr.20130699.