Applied Radiology

CASE SUMMARY

A 42-year-old African-American male presented to the emergency room complaining of diffuse abdominal pain and distention of 2 days duration. Other symptoms included general malaise, nausea, and a few episodes of vomiting. Physical examination revealed a jaundiced male with moderate abdominal distention and tenderness upon palpation of the abdomen. Laboratory data included red blood cell count of 3.59 cells/mm3, hematocrit 23.5% with a MCV 65.3 µm3, white blood cell count of 3.7 cells/mm3, bilirubin 4.5 mg/dL, and elevated alkaline phosphates and hepatic enzymes. Radiographs of the chest (figure 1) and abdomen (figure 2), and CT scans of the chest (figure 3) and abdomen (figure 4) were obtained.

IMAGING FINDINGS

The abdominal radiograph demonstrates hepatosplenomegaly and diffuse osseous changes of widening of the medullary spaces, coarsening of the bony trabeculae, and thickening of the cortices (figure 1). The chest radiograph revealed similar osseous changes, as well as multiple well-defined soft-tissue masses in the posterior aspect of the lung bases (figure 2). Chest CT showed soft-tissue masses in the posterior mediastinal para vertebral region and adjacent to the ribs (figure 3). CT of the abdomen showed similar masses which represent areas of extramedullary hematopoiesis (figure 4). The liver also showed marked increased attenuation compared to the spleen in the absence of IV contrast, compatible with hemochromatosis (figure 4).

DIAGNOSIS

Beta thalassemia (Cooley's) anemia

DISCUSSION

The thalassemias are a diverse group of congenital disorders in which there is a defect in the synthesis of one or more of the subunits of the hemoglobin molecule. Cooley's anemia is the homozygous form, thalassemia minor, and is inherited from one parent. The heterozygous form usually involves only mild anemia and no skeletal stigmata. The homozygous form is the most severe form of the congenital hemolytic anemia and is usually present before 6 months of age with signs and symptoms of severe anemia. Patients have a short life expectancy, the majority dying before reaching adulthood, usually of cardiovascular complications.

Hemoglobin production is decreased with red blood cells that are microcytic and hypochromic. The anemia is produced not only by the patient's inability to synthesize hemoglobin but also by hemolysis, which also leads to the characteristic clinical and radiologic manifestations. The incidence of beta thalassemia is reportedly approximately 7% for the Greek population and 10% in certain Italian populations. However, beta thalassemia can occur in patients of any ethnic background, including Asians and African-Americans.

On physical examination, patients with beta thalassemia are usually pale and may be jaundiced (from hemolysis) or pigmented (from iron overload). Splenomegaly due to extramedullary hematopoiesis can also be seen. Exuberant marrow growth may produce intrathoracic (paraspinal) masses of marrow that can be confused with tumors. Transfusion requirements and con-sequences of iron overload (hemochromatosis), produced in part by chronic transfusion therapy dominate the clinical picture.

Hemochromatosis is identified radiographically as marked increased hepatic attenuation compared to the spleen in the absence of IV contrast. A characteristic appearance is also seen on MRI, with diffuse marked absent signal on both T1- and T2-weighted images. Increased bilirubin production can lead to gallstones and cholecystitis. Cardiac abnormalities include congestive heart failure and arrythmias, which may be an immediate cause of death.

Bone abnormalities include widening of the diploic spaces with coarse trabeculations. In the skull, marked thinning and displacement of the outer table give the skull a "hair on end" appearance. In the peripheral skeleton, the earliest changes are seen in the small bones of the hands and feet, consisting of widened medullary spaces, osteoporosis, thinning of the cortices, and coarsened trabecula. Premature closure of the epiphysis can be seen in approximately 10% of pediatric patients, usually at the proximal humerus and distal femur. Arthropathy is encountered frequently due to hemochromatosis resulting in calcium pyrophosphate deposition arthropathy. In patients in a high risk population with the previously described clinical and radiographic findings, the diagnosis of beta thalassemia is suggested.

The treatment of Cooley's anemia is primarily supportive. The goal of therapy is to administer blood transfusions sufficient to sustain life and prevent skeletal changes, but to avoid the risk of hypertransfusion with serious iron overload. A Hb of 8 to 9 gm/dL appears to be adequate and can be achieved with transfusion of one unit of packed red blood cells every 2 to 3 weeks. Splenectomy is beneficial since it removes the major site of hemolysis, however it is not recommended in the first 4 to 5 years of life because of the risk of overwhelming sepsis in asplenic children. In selected cases, iron chelation therapy is indicated to reverse elevated iron levels due to repeated transfusions.

REFERENCES

1. McGehee HA: Hematologic and neoplastic diseases. In: The Principles and Practice of Medicine, ed 22, pp 325-327. Connecticut, Appleton & Lange, 1988.

2. Juhl JH: Miscellaneous conditions. In: Juhl JH, Crummy AB (eds): Essentials of Radiologic Imaging, ed 6, pp 281-282. Philadelphia, JB Lippincott, 1993.

3. Danhert W: Radiology Review Manual, ed 2, pp 101-102. Baltimore, MD, Williams & Wilkins, 1993.

4. Dunagan WC, Ridner ML: Anemia and transfusion therapy. In: Manual of Medical Therapeutics, ed 22, pp 348-349. Boston, Little, Brown and Company, 1989.

Prepared by Roberto L. Maldonado, MD, Department of Radiology, Jackson County Memorial Hospital, Altus, OK, and Richard G. Barr, MD, PhD, Department of Radiology, St. Elizabeth Health Center, Youngstown, OH.