Immunoglobulin class-switch recombination deficiencies

Table 1 Main characteristics of immunoglobulin class-switch recombination deficiencies

Defect	Relative frequency, percentage	Transmission	CD27⁺ B cells	Somatic hypermutation	Complications
Defect in T cell-B cell cooperation
CD40L	47	X-L	Decreased	Decreased	Opportunistic infections, liver damage
CD40	3	AR	Decreased	Decreased	Opportunistic infections, liver damage
NEMO^a	1	X-L	N or decreased	N or decreased	Opportunistic infections
T_FH defect?	10	?	N	N	Auto-immunity
Intrinsic B-cell defect
AID	10	AR	N	Absent	Lymphadenopathies, auto-immunity
AID co-factor?	12	?	N	N	Lymphadenopathies, auto-immunity
DNA repair defect
Uracil-N-glycosylase	1	AR	N	N (skewed pattern)	Auto-immunity, B lymphomas
Part of a known repair defect: PMS2^a	2	AR	Decreased	N	Cancers
Ataxia telangiectasia^a	2	AR	N	N	Lymphomas, neurological deterioration
DNA repair?	11	AR	Decreased	Decreased	Auto-immunity, B lymphomas, leukemias

^aFrequency could be underestimated because it was sequenced only in patients with obvious symptoms. AID, activation-induced cytidine deaminase; N, normal; NEMO, nuclear factor-kappa-B essential modulator; PMS2, post-meiotic segregation 2; T_fh, T follicular helper.

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