The etiology of anti-GBM disease is thought to be mainly idiopathic, but environmental triggers such as infection, smoking and hydrocarbons have been implicated [1]. In addition, increased risk is associated with HLA-DR15 and DR4 and decreased risk with HLA-DR1 and DR7. Interestingly, HLA-DR15 is associated with an increased risk of MS, which may be of particular relevance in this case as the patient does carry HLA-DRB1*1501 [1].

A recently identified trigger for anti-GBM disease is alemtuzumab, an anti-CD52 monoclonal antibody approved for the treatment of relapsing–remitting MS [2]. Of all MS treatments, alemtuzumab has the longest lasting effect on the immune system [3].

CD-52 is expressed by T and B cells, monocytes, macrophages, and eosinophils [3]. Alemtuzumab is involved in the selective depletion of T and B cells that express CD-52 mainly in the peripheral blood and less so in the lymphoid tissue [3]. Repopulation occurs within weeks with a relative increase in regulatory T cell production and decreased production of pro-inflammatory cytokines [2]. Alemtuzumab has been shown to induce long-term remission of MS after a short treatment course [4].

Despite this, alemtuzumab is associated with delayed secondary autoimmunity [5]. According to the CARE–MS study, the delayed secondary autoimmunity mostly occurred in the form of autoimmune thyroid disease and then autoimmune thrombocytopenia. Autoimmune kidney disease occurred in 0.2% of patients [1]. Both anti-GBM disease as well as membranous nephropathy have been reported. The frequency of autoimmune kidney disease in patients treated with alemtuzumab worldwide is estimated to be 0.13% [1].

The half-life of alemtuzumab is about 2 weeks, and within 30 days of treatment, serum concentrations are generally undetectable [2]. However, most secondary autoimmune events related to alemtuzumab occur months to years after the last infusion, suggesting the mechanism may be related to the initial depletion and repopulation process occurring early in the treatment timeline [2].

One study suggests that autoimmunity after alemtuzumab develops when homeostatic proliferation of T cells dominates the reconstitution process [6]. Homeostatic proliferation is triggered by lymphopenia [7]. Positive and negative selection of T cells that occurs in the thymus creates a group of T cells with differing affinities for self [7]. Some have relatively high self-affinity, though not strong enough to undergo negative selection. These cells are usually quiescent. However, when T cell depletion occurs, homeostatic proliferation of existing T cells occurs, including those that escaped depletion, so the repertoire of T cells may be skewed towards those with high self-affinity [6, 7]. Unfortunately, there are no markers available to identify the risk of secondary autoimmunity in patients [8]. Another theory is that in the repopulation process, B cells repopulate rapidly without initial T cell regulation, potentially promoting autoimmunity [4].

A literature review revealed 12 previous cases of anti-GBM disease after alemtuzumab treatment (Table 1). There seem to be two peaks of disease occurrence: between three and 10 months after the last dose of alemtuzumab; and around 3 years following alemtuzumab. None of the case reports indicated relapsing disease post-recovery. Therefore, this is the first case report of relapsing anti-GBM disease following remission in the context of alemtuzumab treatment.

Anti-GBM disease is usually a monophasic condition. Relapse is uncommon and is usually associated with continued exposure to environmental triggers, such as pulmonary irritants [9]. In this case, it could be surmised that after remission was obtained, the two subsequent UTIs may have revealed sequestered epitopes within the GBM causing recurrence of anti-GBM disease in this already susceptible individual [10]. Due to the rare nature of relapsing disease, current guidelines do not even recommend maintenance immunosuppressive therapy.

Given the risk of secondary autoimmunity, and following the death of one patient in a clinical trial, rigorous monitoring post-alemtuzumab has been proposed. One recommendation is to screen patients for serum anti-GBM antibodies regularly. For the first 48-months post-treatment, it is proposed that kidney and hematological functions are screened monthly, and thyroid function is screened every 4 months [3]. Kidney monitoring involves serum creatinine measurements and urine analysis with microscopy [1].