Lastly, identification of C1q deficiency may facilitate a more rapid diagnosis if found in the context of other clinical features of APDS2 (such as hypogammaglobulinaemia or hyper IgM phenotype, short stature, facial dysmorphia and/or lymphoproliferation) by prompting targeted genetic sequencing for this specific immunodeficiency if next-generation sequencing is not readily available or is associated with long turnaround times. Here, CD40LG is linked to immunodeficiency 36 with lymphoproliferation.