Discussion
IPAF is not really a diagnosis, but a term used for patients with idiopathic interstitial pneumonia and features of autoimmunity who did not fall within the criteria of a connective tissue disease (4). In 2015, a multidiscipinary task force proposed classification criteria for IPAF. Those criteria are organised around features of three domains : a clinical domain consisting of specific extra-thoracic features, a serologic domain consisting of specific autoantibodies, and a morphologic domain consisting of specific chest imaging, histopathology or pulmonary physiologic features (2). According to Fischer et al., our patient had the criteria with an idiopathic interstitial pneumonia based on the CT scan, ANA > 1 :320 titre (anti-RNP and anti-JO1 identification) and diffuse polyarthralgia. Furthermore, all alternative etiologies were excluded and he did not meet criteria of a defined connective tissue disease. We also note that CK levels were in standards and the patient did not present myalgia despite positive anti-JO1 identification.
There is no specific treatment as IPAF is a research consensus statement and not a well-defined entity. Management consists of global care with pulmonary rehabilitation, oxygen therapy if necessary, prevention of infection and bone health assessment (1). Corticosteroids and immunosuppressive agents are usually used. For example, azathioprine and mycophenolate mofetil (MMF) are associated with improvement or stabilization of lung function (1). In this case, the patient received a combination of corticosteroids and MMF but this was not enough. He was considered as a patient with refractory interstitial lung disease (ILD) and Rtx treatment was given as salvage therapy with an improved therapeutic response. A retrospective study indicates efficacy of Rtx in patients with Antisynthetase Syndrome (AS) and ILD. Indeed, this study demonstrated a reduction in ILD extent post therapy (5). Doyle et al. also showed that in ILD with AS, the principal indication for Rtx use was recurrent or progressive ILD due to failure of other agents resulting in stability or improvement in pulmonary function or severity of ILD on CT scan with a good tolerance of the treatment (6).
In 2012, Keir et al. showed the benefits of using Rtx as life-saving therapeutic intervention in severe CTD-ILD with failure to conventional immunosuppression. In his study, patients improved pulmonary function with Rtx (3). In 2016, Lepri et al. demonstrated that Rtx may help to control the course of ILD in CTD producing a stabilisation of lung involvement in systemic sclerosis and mixed connective tissue disorders (7).
According to Saunders et al., there are no approved therapies for CTD-ILD : cyclophosphamide is the main therapy for patient with severe or progressive CTD-ILD but observationnal studies suggested that Rtx is an effective rescue therapy for refractory CTD-ILD (8).
Recently, Atienza-Mateo et al. demonstrated that Rtx was a good therapeutic option to preserve lung fonction in patients with IPAF (9).