Haematological complications of X-linked lymphoproliferative syndrome type 1 and 2
Authors: Roppelt A. A. , Laberko A. L. , Burlakov V. I. , Kan N. Yu. , Rodina Yu. A. , Yukhacheva D. V. , Viktorova E. A. , Selezneva O. S. , Pershin D. E. , Vedmedskaya V. A. , Raykina E. V. , Varlamova T. V. , Кieva A. M. , Mann S. G. , Polyakov A. V. , Sermyagina I. G. , Petrova U. N. , Kalinina I. I. , Shelikhova L. N. , Balashov D. N. , Kondratenko I. V. , Maschan A. A. , Shcherbina A. Yu. 
Published: October 2020

X-linked lymphoproliferative syndrome type 1 (XLP1) and 2 (XLP2) are primary immunodeficiencies (PID), combined in one group because of shared abnormal response to Epstein–Barr virus (EBV) and caused by mutations in SH2D1A and XIAP genes, respectively. Hemophagocytic lymphohistiocytosis (HLH) is a frequent life-threatening complication of both diseases. We analyzed haematological complications, such as HLH and cytopenia, in 12 patients with XLP1 and 11 – with XLP2. The research was approved by Independent ethic committee and the academic board of Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology (Moscow, Russia). Analyzed were patients who were treated or consulted in Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology (Moscow, Russia) since 2012 and in Russian Clinical Children's Hospital (Moscow, Russia) since 2003 to February 2020. 19 XLP1 patients from 13 families and 16 XLP2 patients from 14 families were included. For patients with haematological complications XLP diagnosis was based on the ESID criteria and genetically confirmed in 19 cases by detecting mutations in SH2D1A or XIAP gene (8 XLP1 and 11 XLP2 patients). Intracellular expression of corresponding SAP and XIAP proteins was performed by intracellular staining of SAP/XIAP in lymphocytes. Genetic analysis to detect mutations in SH2D1A and XIAP genes was performed by the Sanger sequencing method on Genetic Analyzer 3130х1 (Applied Biosystems, USA) according to the manufacturer protocol, or by the Multiplex Ligation-Dependent Probe Amplification method using SALSA MLPA Probemix P205 SH2D1A-XIAP-ITK (MRC-Holland, the Netherlands), or by the next-generation sequencing (NGS) method on NextSeq (Illumina) platform using a paired end tag (PET) sequencing method. Varying degree of cytopenia was present in 4 patients with XLP1 and 2 – with XLP2. None of XLP1 patients with cytopenia, and all XLP2 patients with cytopenia subsequently developed full HLH. Overall 8 XLP1 and 11 XLP2 patients developed HLH. HLH-associated mortality before hematopoietic stem cell transplantation (HSCT) was 75% in a group of XLP1 patients and 0% – in XLP2. HSCT was performed in 3 XLP1 patients, which was not sufficient for survival analysis and in 9 XLP2 patients, in whom overall survival was 74%. HLH is the most often haematological complication of XLP1 and XLP2. Fulminant HLH in XLP1 requires early and aggressive treatment. In XLP2 patients HLH remission can be reached on mono- or bicomponent immunosuppressive therapy which allows to reduce therapy-associated toxicity. In XLP2 patients cytopenia can precede HLH, while in XLP1 patients cytopenia is probably caused by other mechanisms. HSCT is a curative treatment for XLP1 and 2 which should be considered as soon as the diagnosis is made.