Clinical Meetings at RH Year 2013

2013 Sept- A patient with abnormal chest X-ray

Dr CHENG Man Fung, Dr TANG Sze Wan, and Dr TSE Pak Yiu

Department of Medicine, Tseung Kwan O Hospital

History

A 47-year old lady was referred from chest clinic to respiratory clinic in Tseung Kwan O Hospital because of finding of chest X-ray abnormality during contact investigation for tuberculosis.

She had history of Hb H disease, protein S deficiency and proteinuria, and was previously followed up in another hospital. She had splenectomy done in 2002. Before the operation, her hemoglobin level was about 6-8 g/dL, and she required blood transfusion. After splenectomy, her hemoglobin was about 9-10 g/dL and she did not require transfusion. Her last chest X-ray in 2002 in another hospital was commented as normal. She was on folic acid supplement.

The patient’s domestic helper was recently diagnosed to have tuberculous lymphadenitis and the patient then attended chest clinic for contact investigation. She had occasional cough with whitish sputum for two months. There was no fever, night sweat, weight loss, shortness of breath, hemoptysis, chest pain or back pain. There was no acid reflux or dysphagia and there was no neurological complaint. Physical examination revealed mild pallor. There was no cervical lymphadenopathy. No finger clubbing was detected. Chest, abdominal and neurological examination was unremarkable.

Complete blood count showed hemoglobin level of 9.4 g/dL, MCV 68.8fL, MCH 18.5pg, RDW 22.3%, WBC 8.9 x10⁹ /L and platelet 390 x10⁹/L. Sputum for cytology was negative. The chest X-ray showed bilateral intrathoracic well circumscribed masses in mid-thorax. The CT scan thorax with contrast revealed bilateral intra-thoracic extrapleural paravertebral lobulated masses extending from about T6 to T10 levels. The masses showed soft tissue density with contrast enhancement. There was prominent fat component along the periphery of right sided lesion. There was no associated bony erosion at adjacent rib and vertebral body. MRI thorax showed similar bilateral paravertebral mass which appeared enhancing on contrast injection. The right side lesion was heterogenous in appearance with suggestion of fatty component.

Diagnosis of extramedullary hematopoiesis was made based on clinical history and radiological features.

Discussion

Hb H disease is found in many parts of the world. It is particularly prevalent in Southeast Asia and in Southern China.¹ The incidence of Hb H disease in Hong Kong is approximately 6 in 10000 live births.² Although Hb H disease is generally believed to be a mild disorder, there is a marked phenotypic variability, ranging from asymptomatic, to need for periodic transfusions, to severe anemia with hemolysis and hepatosplenomegaly, and even to fatal hydrops fetalis syndrome in utero.³ Treatment is primarily preventive and supportive. Folic acid supplement is usually recommended. Oxidative compounds and unnecessary iron therapy should be avoided.³ Monitoring for possible iron overload and related organ dysfunction is recommended.² In patients with marked splenomegaly and hypersplenism, splenectomy can result in significant hematologic and clinical improvements.³

Extramedullary hematopoiesis is the ectopic development of hematopoietic tissue outside the bone marrow. It is a compensatory mechanism by which the body tries to maintain a level of erythrogenesis sufficient for its demand. It usually occurs in patients with thalassemia, but may also be found in patients with leukemia, hemoglobinopathies and myelofibrosis.⁴

There have been only few reported cases of Hb H disease with intrathoracic extramedullary hematopoiesis.^5-7

Non-invasive diagnostic procedures are advocated to establish the diagnosis of extramedullary hematopoiesis ^6,8,9,11 because the masses of extramedullary hematopoiesis are highly vascular and biopsy can cause dangerous hemorrhage or even a fatal outcome.¹⁰ Non-invasive investigations include contrast enhanced computed tomography, magnetic resonance imaging of the thorax, technetium-99 sulphur colloid radionuclide bone marrow scanning.^6,8,9 Tissue biopsy and/or surgical resection are reserved for those cases where extramedullary hematopoiesis is not suspected or when complications require surgical intervention.⁹

Intrathoracic extramedullary hematopoiesis is most often seen as paravertebral mass lesions. Other disorders of the posterior mediastinum such as neurogenic tumor should be considered. Characteristic features helpful in recognizing intrathoracic extramedullary hematopoiesis on chest X-ray and CT scan thorax include widening of the ribs most marked at the vertebral end, presence of unilateral or bilateral well-circumscribed lobulated, paravertebral mass lesions usually caudal to the sixth thoracic vertebrae, absence of bony erosion in the vertebral body, and the presence of adipose tissue within the mass. ⁹

Active recent haematopoietic extramedullary lesions have rich vasculature while inactive older lesions have fatty replacement or iron deposit.¹² Active haematopoietic lesion showed soft tissue CT density, intermediate signal intensity in both T1 and T2-weigthed MR images and some enhancement after contrast medium intravenous administration. Older inactive lesions have increased CT density due to iron deposit or low density due to fatty infiltration. MRI show high signal intensity in both T1 and T2 weighted MR images due to fatty infiltration or low signal intensity in both T1 and T2 weighted MR images due to iron deposition.¹² Features of activity and inactivity are observed in our patient.

Reference

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