Deciding on which are the best investigations and treatment modalities is a difficult task. We described a case of pulmonary nocardiosis with needle tract seedling to the pectoralis major muscle after receiving rituximab for refractory rheumatoid arthritis.
Rituximab, a B-cell-depleting monoclonal anti-CD20 antibody, was approved by the Malaysian Drug agency in 2007. There are limited local data on the side effect of rituximab. REFLEX1
has shown that serious infections occurred in only 5.2% of the patient population who received rituximab, compare to 3.7% of those in the placebo category. However, there was no report on occurrence of opportunistic infections during the 24 weeks of the study. According to Salliot et al
respiratory tract bacterial infection is the main mode of serious infection, as illustrated in our case. The meta-analysis also did not show significant occurrence of opportunistic infections.
sp., is a Gram-positive bacillus, aerobic actinomycetes in the genus Nocardia
sp., with partial acid-fastness. Partial acid-fastness is a unique characteristic of Nocardia
sp. that is not exhibited by other actinomycetes. There are more than 50 known species, and more than 50% of them cause infections in humans.3
are known to cause infection predominantly in humanss.4
It is an opportunistic infection in immunocompromised patients. Its main route of acquisition is through aerosol, which explains why lungs are a primary site of infection in more than two-thirds of cases reported.5 6
Other modes of infections are ingestion of contaminated food products and direct inoculation from trauma. In the case of our patient, she possibly acquired the infection through aerosol route, which later disseminated to the chest wall after needle lung biopsy.
Nocardiosis occurs in people with depressed cellular immunity. The risk factors for acquisition of the disease are usage of long-term glucocorticoids, immunosuppressive therapy, underlying lung disease, lymphoproliferative diseases, transplantation, and AIDS. It is possible that our patient had already acquired the nocardiosis prior to initiation of rituximab. The immunosuppressive effects of rituximab had caused a rapid, accelerated growth of nocardiosis. The haematological side effects of rituximab also lead to T-cell dysfunction via bone marrow, which included hypoplasia, lymphopenia, neutropenia and leucopenia.
During our literature search, we have noted that there were a few reported cases of nocardiosis post-rituximab. From this search, we also noted that there were two reported cases with pulmonary nocardiosis as in the case of our patient. In addition, there were also two cases of lymphoproliferative disease which may contribute to lymphocytes dysfunction leading the nocardiosis. A wide variety of immunosuppressant therapy had been given to the three patients as stated in . From these cases, the patient's underlying immunosuppression from the underlying co-morbidity posed a confounding factor for the development of nocardiosis. We can suppose that the more immunosuppressed the patient is, the higher the risk of acquiring nocardiosis.
Summary of published Cases of Nocardiosis Post-Rituximab.
The treatment of choice of Nocardia sp. infections is Trimethoprim-sulfamethoxazole. As we can see from the list of reported cases, two responded to TMP-SMX, as was the case with our patient.
The lesson to learn here is that opportunistic infection should always be anticipated in an immunocompromised host. The delay in diagnosing a dire infection can render a patient in danger. Thus, the benefit versus the complication of treatment or investigation should always be considered carefully.
- Rituximab is a potent immunosuppressive agent.
- Opportunistic infections may appear with the use of biologic therapy.
- A close surveillance of infection must always be done in a patient receiving immunosuppressive therapy.