The immunosuppressed patient

Published on 03/04/2015 by admin

Filed under Hematology, Oncology and Palliative Medicine

Last modified 03/04/2015

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The immunosuppressed patient

Many patients with blood disorders are immunosuppressed. Patients with aggressive haematological malignancies such as leukaemia and non-Hodgkin’s lymphoma have their immune function initially compromised by the disease and then further depressed by chemotherapy. Others have more subtle deficiencies. Patients with ‘benign’ diseases such as immune thrombocytopenia (ITP) and hereditary spherocytosis who have had splenectomy performed are also at increased risk of infection.

An increased susceptibility to infection can arise from multiple factors (Table 43.1). Neutropenia and neutrophil dysfunction are probably the most important causes of infectious complications in patients with leukaemia. Unlike many other forms of immunosuppression, neutropenia is easy to quantify – the risk of infection rises appreciably at counts below 0.5 × 109/L and is greatest where the count is below 0.1. Lymphopenia and lymphocyte dysfunction are seen in lymphoid malignancy and after chemo- and radiotherapy. Defects in humoral immunity are particularly seen in patients with chronic lymphoid malignancies and in myeloma. The likelihood of infection is related to the severity of hypogammaglobulinaemia.

Other common immunosuppressive factors are the loss of mucosal or skin integrity due to damage from disease or treatment, and the presence of indwelling venous catheters.

Types of infection

Bacteria

Bacterial infections in neutropenic patients are often caused by the spread of commensal flora to previously sterile sites. Fatal septicaemia can result from Gram-negative bacilli such as Pseudomonas aeruginosa, E. coli, Klebsiella spp. and Enterobacter spp. Gram-positive cocci currently cause the majority of documented bacteraemias. The skin pathogen Staphylococcus epidermidis often colonises indwelling venous catheters. The use of broad-spectrum antibiotics can lead to the emergence of toxin-producing Clostridium difficile in the stools. Methicillin-resistant Staph. aureus (MRSA) and bacteria producing extended-spectrum beta-lactamases (ESBLs) leading to antibiotic resistance are becoming increasingly problematic in hospitals.

Bacterial infection in neutropenic patients may be overt – for instance a chest infection with a productive cough or the presence of infected skin lesions (Fig 43.1). However, bacterial sepsis can equally present with non-specific malaise and a pyrexia. In the latter case extensive cultures including blood, nose, throat, stool and urine are indicated.

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