Rare solid tumors in a patient with Wiskott-Aldrich syndrome after hematopoietic stem cell transplantation: case report and review of literature

Background and aims

Wiskott-Aldrich syndrome (WAS) is an X-linked recessive primary immunodeficiency disorder characterized by severe eczema, recurrent infections, and micro-thrombocytopenia. Allogeneic hematopoietic stem cell transplantation (HSCT) is a potentially curative therapeutic option for patients with classic form. The risk of developing post-transplant tumors appears to be higher in patients with WAS than in other inborn errors of immunity (IEIs), but the actual incidence is not well defined, due to the scarcity of published data.

Methods

Herein, we describe a 10-year-old patient diagnosed with WAS, treated with HSCT in the first year of life, who subsequently developed two rare solid tumors, kaposiform hemangioendothelioma and desmoid tumor. A review of the literature on post-HSCT tumors in WAS patients has been performed.

Results

The patient received diagnosis of classic WAS at the age of 2 months (Zhu score = 3), confirmed by WAS gene sequencing, which detected the nonsense hemizygous c.37C>T (Arg13X) mutation. At 9 months, patient underwent HSCT from a matched unrelated donor with an adequate immune reconstitution, characterized by normal lymphocyte subpopulations and mitogen proliferation tests. Platelet count significantly increased, even though platelet count never reached reference values. A mixed chimerism was also detected, with a residual WASP- population on monocytes (27.3%). The patient developed a kaposiform hemangioendothelioma at the age of 5. A second abdominal tumor was identified, histologically classified as a desmoid tumor when he reached the age of 10 years. Both hematopoietic and solid tumors were identified in long-term WAS survivors after HSCT.

Conclusion

Here, we describe the case of a patient with WAS who developed two rare solid tumors after HSCT. An active surveillance program for the risk of tumors is necessary in the long-term follow-up of post-HSCT WAS patients.

Immune tolerance breakdown in inborn errors of immunity: Paving the way to novel therapeutic approaches

Up to 25% of the patients with inborn errors of immunity (IEI) also exhibit immunodysregulatory features. The association of immune dysregulation and immunodeficiency may be explained by different mechanisms. The understanding of mechanisms underlying immune dysregulation in IEI has paved the way for the development of targeted treatments. In this review article, we will summarize the mechanisms of immune tolerance breakdown and the targeted therapeutic approaches to immune dysregulation in IEI.

Epigenetic Alterations in Inborn Errors of Immunity

The epigenome bridges environmental factors and the genome, fine-tuning the process of gene transcription. Physiological programs, including the development, maturation and maintenance of cellular identity and function, are modulated by intricate epigenetic changes that encompass DNA methylation, chromatin remodeling, histone modifications and RNA processing. The collection of genome-wide DNA methylation data has recently shed new light into the potential contribution of epigenetics in pathophysiology, particularly in the field of immune system and host defense. The study of patients carrying mutations in genes encoding for molecules involved in the epigenetic machinery has allowed the identification and better characterization of environment-genome interactions via epigenetics as well as paving the way for the development of new potential therapeutic options. In this review, we summarize current knowledge of the role of epigenetic modifications in the immune system and outline their potential involvement in the pathogenesis of inborn errors of immunity.

Improved dual AAV vectors with reduced expression of truncated proteins are safe and effective in the retina of a mouse model of Stargardt disease

Stargardt disease (STGD1) due to mutations in the large ABCA4 gene is the most common inherited macular degeneration in humans. We have shown that dual adeno-associated viral (AAV) vectors effectively transfer ABCA4 to the retina of Abca4-/- mice. However, they express both lower levels of transgene compared with a single AAV and truncated proteins. To increase productive dual AAV concatemerization, which would overcome these limitations, we have explored the use of either various regions of homology or heterologous inverted terminal repeats (ITR). In addition, we tested the ability of various degradation signals to decrease the expression of truncated proteins. We found the highest levels of transgene expression using regions of homology based on either alkaline phosphatase or the F1 phage (AK). The use of heterologous ITR does not decrease the levels of truncated proteins relative to full-length ABCA4 and impairs AAV vector production. Conversely, the inclusion of the CL1 degradation signal results in the selective degradation of truncated proteins from the 5'-half without affecting full-length protein production. Therefore, we developed dual AAV hybrid ABCA4 vectors including homologous ITR2, the photoreceptor-specific G protein-coupled receptor kinase 1 promoter, the AK region of homology and the CL1 degradation signal. We show that upon subretinal administration these vectors are both safe in pigs and effective in Abca4-/- mice. Our data support the use of improved dual AAV vectors for gene therapy of STGD1.

5-Fluorocytosine and Candida yeasts

The authors report 5-fluorocytosine's activity against 101 Candida albicans and 42 Candida non-albicans strains. They point out the drug's lower inhibitory and lethal activity against Candida non-albicans. A 1.56 microgram/ml concentration inhibits 83% of Candida albicans while only 40% of Candida non-albicans is inhibited.