Case report An MHC class II deficient 2-year-old boy presented with fever and an enlarging left neck mass 100 days post allogeneic haematopoietic stem cell transplant (HSCT). Fever persisted despite treatment with broad-spectrum β-lactam antibiotics. His BCG vaccination site at presentation was quiescent. Ultrasound showed enlarged cervical lymph nodes. An incisional biopsy of the large nodal mass yielded acid-fast bacilli, identified as Mycobacterium bovis by genome sequencing. Treatment with rifampicin, isoniazid and pyridoxine was started. The mass suppurated (figure 1), before healing concurrently with T-lymphocyte reconstitution at approximately day 130 post-HSCT.
BCG infection can complicate vaccination in patients with severe combined immunodeficiencies (SCID), including MHC II deficiency1 1causing a spectrum ranging from simple adenitis to disseminated disease. BCG immune reconstitution inflammatory syndrome, typically presenting as localised adenitis ipsilateral to vaccination site, is well-described after commencing antiretroviral therapy for HIV and is recognised in patients post-HSCT.22 3 2 33In this case, T-lymphocyte reconstitution restoring the T-lymphocyte mediated response in a previously BCG-vaccinated child is likely to have precipitated both this presentation and its resolution.
Early identification of SCID though newborn screening might prevent vaccine administration to patients at risk of complications.
How is MHC class II deficiency inherited?
What role do MHC class II molecules have in the immune response?
Costimulation of naïve CD4+ T-helper lymphocytes to prevent anergy
Initiation of immunoglobulin class-switch recombination in B-lymphocytes
Presentation of antigen to naïve CD4+ T-lymphocytes
Presentation of antigen to naïve CD8+ T-lymphocytes
Which method has been proposed for newborn screening for SCID in the UK?
Absolute lymphocyte count
Detection of T-lymphocyte receptor excision circles (TRECs)
Tandem mass spectrometry to detect toxic metabolites
Immunoassay for CD3 and CD45
Which is the most appropriate treatment for localised BCG disease in immunocompromised children?
Rifampicin and isoniazid
Surgical resection and instillation of isoniazid
Rifampicin, isoniazid, ethambutol and pyrazinamide
What common side-effect should patients receiving isoniazid be counselled for?
Increased seizure frequency
Acute kidney injury
Change in colour of urine
Questions Answers can be found on page 2.
- cell biology
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Contributors CT and ISvdL hold joint lead authorship. CT and ISvdL conceived the project, collated the relevant data and produced the draft manuscript. EW, SO, MS, AG and SP provided clinical data and critical review.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.