Atypical HLA class I deficiencies are characterized by less severe reduction in surface expression of HLA class I molecules (approximately tenfold). It is called atypical due to absence of clinical symptoms, and if present, it will be transient or moderate. It includes very heterogenous group due to heterogenous molecular defects that are present in this type. Patient with atypical HLA class I deficiency will have a homozygous HLA genotype and evidence of a transporter associated with antigent processing 2 deficiency. Thus transporter associated with antigen deficiency may lead to variably severe reductions in the surface levels of HLA class I molecules.