acquired

Last reviewed 01/2018

This uncommon disease tends to affect adults over the age of 50 years.

Infections such as the following can cause red cell aplasia

• HIV infection
• atypical pneumonia
• infectious mononucleosis
• mumps
• viral hepatitis

Some medications associated with development of red cell aplasia include:

• antiepileptic medications (eg, phenytoin, carbamazepine, sodium valproate)
• mycophenolate
• azathioprine
• chloramphenicol
• sulphonamides
• isoniazid
• clopidogre

Thymoma associated acquired primary red cell aplasia

• thymoma, a rare epithelial neoplasm, is the most common anterior-superior mediastinal tumour
  • based on the appearance of neoplastic epithelial cells, the World Health Organization (WHO) has classified thymoma as type A (spindle or oval cells), type B (dendritic or epithelioid cells), and type C (exhibiting combined features of types A and B)
  • thymoma can occur sporadically or in association with other conditions, such as myasthenia gravis, pure red cell aplasia (PRCA), and hypogammaglobulinemia (1)
    
    
• only 5% of thymoma cases develop PRCA. However, 10-50% of patients presenting with PRCA have an associated spindle cell type thymoma (2)
  
  
• PRCA is characterised by failure of erythropoiesis, with preserved granulopoiesis and megakaryopoiesis
  • thymoma complicated by PRCA is associated with a poor outcome, and thymectomy provides a low PRCA remission rate in such patients
    • hence, possible onset of PRCA should be anticipated, and close follow-up of these patients is recommended

Of patients with red cell aplasia:

• females predominate (2:1) in the thymoma group
• males dominate in the group without a thymoma
• 25-30% of patients undergo remission when the thymoma is removed. It is thought that the specific inhibition of red cell production is autoimmune-mediated - autoantigens include erythropoietin (1)
• exploratory thoracotomy is undertaken only when x-ray or CT scan show evidence of thymic enlargement.

Notes:

• most cases of acute transient primary red cell aplasia are caused by parvovirus B19 infection
  • parvovirus 19 infections can persist longer in immunocompromised patients.

Reference:

• Handa SI, Schofield KP, Sivakumaran M, Short M, Pumphrey RSH. Pure red cell aplasia associated with malignant thymoma, myasthenia gravis, polyclonal large granular lymphocytosis and clonal thymic T cell expansion. J Clin Pathol. 1994;47:676-679.
• Lahiri TK, Agarwal D, Agarwal K, Shukla J. Pure red cell aplasia associated with Thymoma. Indian J Chest Dis Allied Sci. 2002;44(4):259-262.
• Sawada K, Fujishima N, Hirokawa M. Acquired pure red cell aplasia: updated review of treatment. Br J Haematol. Aug 2008;142(4):505-14
• Li G, Li ZQ, Yang QY, Yang JD. Acquired pure red cell aplasia due to treatment with clopidogrel: first case report. J Thromb Thrombolysis. Dec 3 2013
• Casadeval, N. et al.. Autoantibodies against erythropoietin in a patient with pure red cell aplasia. NEJM 1996;334(10): 630-3.
• Thompson DF, Gales MA. Drug-induced pure red cell aplasia. Pharmacotherapy. Nov-Dec 1996;16(6):1002-8.