Extramedullary Hematopoiesis: Breathtaking and Hair-Raising

To the Editor: Thoracic masses due to extramedullary hematopoiesis are rare, occurring most often in patients with thalassemia or congenital hemolytic anemia.1 The masses usually cause no symptoms but can cause pleural effusion or hemothorax. Here, we describe a patient with respiratory insufficiency caused by large, hematopoietic thoracic masses. 

A 51-year-old woman with type III congenital dyserythropoietic anemia2 (diagnosed in 1971, with lifelong anemia) was referred to our clinic in December 1998 because of exertional dyspnea and respiratory insufficiency. In 1980, a routine radiograph of the chest had shown a small, right-sided thoracic mass; biopsy had revealed extramedullary hematopoiesis. In November 1998, the patient had had bilateral pleural effusions and was treated with thoracentesis and pleurodesis. 

At referral, when her condition was clinically stable, she had persistent hypercapnia and severely restrictive lung function (forced vital capacity, 0.84 liter; forced expiratory volume in one second, 0.66 liter) Her hemoglobin concentration was 7.6 g per deciliter. Radiographs and computed tomographic (CT) scans of the chest showed large paravertebral masses that deformed and stretched the lower-lobe bronchi in both lungs (Figure 1A). The right mass measured 17 by 12 cm, and the left 15 by 12 cm. A single-photon-emission CT (SPECT) scan of the bone marrow obtained after injection of technetium-99m sulfur colloid revealed accumulation of the radionuclide in both masses. Superimposition of the SPECT image of the bone marrow on the CT scan of the chest confirmed that the thoracic masses contained hematopoietic cells. The bone marrow scan also showed enlargement of the liver and spleen and accumulation of hematopoietic cells in the extremities, the sternum, the ribs, and the skull. This accumulation caused an extreme "hair-on-end" phenomenon on the radiograph of the skull (Figure 1B).

Extramedullary hematopoiesis can be treated with frequent blood transfusions to limit the hematopoietic stimulus. In addition, hydroxyurea therapy has been reported to decrease the size of masses of hematopoietic cells and to relieve spinal cord compression,3 as well as to reduce the size of cutaneous masses.4 We treated our patient with blood transfusions and hydroxyurea (500 mg twice daily). During a four-month treatment period, her clinical condition gradually improved, her forced vital capacity and forced expiratory volume in one second increased,4 her blood gas values normalized, and the thoracic masses decreased slightly in size. 

Extramedullary hematopoiesis has been reported in an asymptomatic patient with type II congenital dyserythropoietic anemia.5 Our patient had respiratory insufficiency due to paravertebral extramedullary hematopoiesis, and treatment with blood transfusions and hydroxyurea resulted in a satisfactory clinical, functional, and radiologic response

Nguồn: nejm

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