Bone Marrow Transplant for Severe Combined immunodeficiency Patients: Experience of Malaysia
Intan Hakimah Ismail
Consultant Paediatrician, Clinical Immunologist and Allergist
Heads of Department and Clinical Immunology Unit, Department of Paediatrics,
Faculty of Medicine and Health Sciences, Universiti Putra Malaysia
Primary immunodeficiencies (PID) refer to a heterogeneous group of disorders characterised by poor or absent function in one or more components of the immune system. Severe Combined Immunodeficiency (SCID) is one of the most severe forms of PID. It is characterised by genetic defects involving absence of both T-lymphocyte and B-lymphocyte function which results in lymphopenia and hypogammaglobulinaemia. In many cases it also involves natural killer lymphocyte function. Affected infants often appear normal at birth but subsequently develop severe infections early in life due defects in humoral and cellular immunity, and if untreated, result in a fatal outcome within the first 2 years of life. Unfortunately, most children are diagnosed only after the occurrence of severe and recurrent infections and their complications, with a significantly worse prognosis.
Bone marrow transplantation (BMT) using stem cells obtained from a family-related, HLA-identical donor is currently the established mode for immune restitution and cure for children with SCID. Therefore, identification of SCID is considered a paediatric emergency because survival depends on expeditious stem cell reconstitution as patients transplanted before age 3.5 months have more than 90% survival rate. Delay in recognising and detecting SCID can have fatal consequences and also reduces the chances of a successful haematopoietic stem cell transplant (HSCT).
However, the medical challenge is compounded by the absence of an HLA-matched sibling which occurs in 70-80% of individuals. Stem cell transplant using an HLA-partially matched family donor, also referred to as haploidentical transplants, are increasingly being utilised. The first HLA-matched sibling BMT for SCID was performed in Malaysia in 2002, whereas the first haploidentical parental HSCT (using a T-cell depleted graft) for SCID was performed in 2015. Between April 2016 and December 2017, three patients with SCID underwent T-cell-replete haploidentical transplants from a parental donor and one patient received an HLA-matched sibling HSCT, all with good outcomes.
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