A 15-year-old black male with known sickle cell anemia (SS disease) comes to the emergency room because of a slight cough and shortness of breath for 24 hours. He has had some chest pain with deep breathing and some minor pain in his leg and lower abdomen from hip replacement surgery for avascular necrosis of the femoral head 10 days ago. He has a 102 degree F fever. His past medical history shows previous admissions for pain crises. He smokes tobacco. His pertinent physical examination shows a respiratory rate of 30 with shallow breaths, and splinting with deep breaths. He was slightly pale. His heart examination had a grade II/IV systolic murmur best at the lower left sternal border and heard over the precordium. Lung exam reveals good aeration with decreased breath sounds at the left lower lung fields. There was no wheezing but possibly fine crackles. His abdomen and musculoskeletal examination are normal except for a healing surgical incision. The laboratory evaluation reveals a hemoglobin of 6.5 mg/dl, hematocrit of 18%, platelets of 391,000 mm2 and a WBC count of 18,000 mm2 with a slight left shift. PTT was 15 seconds and his INR (international normalized ratio) was 1.4 (normal up to 1.3). Blood
and urine cultures were sent and eventually had no growth. His chest x-ray showed a left lower lobe infiltrate. His pulse oximeter was 88%. A clinical diagnosis of acute chest syndrome was made. He was treated and recovered after 1 week. He was counseled about his increased risk of complications with tobacco smoking.
Figure 1 – 11-01-04 – PA and lateral radiographs of the chest showing Acute Chest Syndrome. Notice the left lower lobe infiltrate.
Sickle Cell Disease (SCD) is a group of genetic disorders with >50% of sickle hemoglobin and some degree of hemolytic anemia. The cause is a mutation on the short arm of chromosome 11 that results in changes to the beta-hemoglobin chain.
(Hemoglobin is made up of 2 alpha chains and 2 beta chains.) It affects males and females equally. Hemoglobin S is the most common and clinically severe. SCD occurs worldwide and in the US occurs in 1:4000 newborns and 1:375 African-Americans. Patients are often treated by the cooperative efforts of local health care providers and comprehensive treatment centers. Treatment includes prophylaxis for infection, early recognition of complications, and rehabilitation. Newer therapies are being used in some patients including bone marrow transplantation and hydroxyurea or other agents to induce fetal hemoglobin.
Figure 2 – 11-01-04 – Diagram showing sickled cells from the National Human Genome Research Institute.
The complications of SCD are categorized into 5 major categories: infections, splenic sequestration, aplastic crisis, vasoocclusive or pain episodes and acute chest syndrome. These complications often occur concurrently. Acute chest syndrome is defined as fever, chest pain, tachypnea and hypoxia with a new pulmonary infiltrate. The infiltrate often will begin in one lobe and progress to other lobes. Triggers include hypoxemia, hemoconcentration, and acidosis.
Patients may quickly progress to respiratory failure and need intubation. Treatment includes oxygen therapy (to treat hypoxemia), red blood cell transfusions or exchange transfusions (to increase the oxygen carrying capacity and decrease the amount of sickle hemoglobin), hydration (to decrease sickling), antibiotics (to treat infection especially for Streptococcus pneumoniae, Mycoplasma, and Chlamydia), chest physiotherapy (for pulmonary toilet), and pain control. Acute chest syndrome is the leading cause of death for adults and adolescents with SCD. Fifteen percent of children born with SCD die by age 20.
Avascular necrosis of the femoral head occurs in patients with SCD because of vascular occlusion, infarction and collapse at the site. Up to 30% have hip pathology by 30 years. Risks of arthroplasty include a relatively high rate of infection and problems with the prothesis requiring reoperation including the risks of anesthesia.
This patient met the clinical diagnosis for acute chest syndrome. However, because of his recent surgery, the differential diagnosis of his shortness of breath was broadened initially to include:
- Acute chest syndrome
- Pulmonary embolus
- Thromboembolism because of immobility
- Fat embolism because of bone marrow infarction
- Sepsis – from SCD or wound
Other causes of shortness of breath that are much less likely in this patient could include:
- HIV with lymphoid interstitial pneumonia (LIP)
- Heart failure
- Foreign body
As his physical examination had no signs of thromboembolism, he had normal laboratories and his chest x-ray was not suggestive of a pulmonary embolism, it was believed that pulmonary embolism was lower on the differential diagnosis. The patient was treated for acute chest syndrome including antibiotics for sepsis and pneumonia and
chest physiotherapy for atelectasis. He was monitored throughout his course for response to therapy and the possibility of thromboembolism.
Questions for Further Discussion
1. What prophylactic treatments should young children with SCD receive?
2. What are the advantages and disadvantages of bone marrow transplant for SCD patients?
3. What are some of the common presentations of vasoocclusive disease?
To Learn More
To view pediatric review articles on this topic from the past year check PubMed.
The Management of Sickle Cell Disease. National
Institutes of Health National Heart, Lung, and Blood Institute Division of Blood Diseases and Resources NIH PUBLICATION NO. 02-2117 (revised 6/2002). Available from the Internet at: http://www.nhlbi.nih.gov/health/prof/blood/sickle/index.htm (cited 10/14/04)
Rudolph CD, et.al. Rudolph’s Pediatrics 21st edit. McGraw-Hill, New York, NY. 2003.
Pegelow C. Sickle Cell Anemia. eMedicine.
Available from the Internet at http://www.emedicine.com/ped/topic2096.htm.(rev. 6/24/04, cited 10/14/04).
Donna M. D’Alessandro, MD
Associate Professor of Pediatrics, Children’s Hospital of Iowa
November 1, 2004