Allergology International. 2012;61:207-217 ! DOI: 10.2332 allergolint.12-RAI-0446 REVIEW ARTICLE Review Series: Primary Immunodeficiency and Related Diseases Diagnosis and Treatment in Anhidrotic Ectodermal Dysplasia with Immunodeficiency Tomoki Kawai1, Ryuta Nishikomori1 and Toshio Heike1 ABSTRACT Anhidrotic ectodermal dysplasia with immunodeficiency (EDA-ID) is characterized according to its various manifestations, which include ectodermal dysplasia, vascular anomalies, osteopetrosis, and diverse immu- nological abnormalities such as susceptibility to pathogens, impaired antibody responses to polysaccharides, hypogammaglobulinemia, hyper-IgM syndrome, impaired natural killer cell cytotoxicity, and autoimmune dis- eases. Two genes responsible for EDA-ID have been identified: nuclear factor-κ B(NF-κ B) essential modula- tor (NEMO) for X-linked EDA-ID (XL-EDA-ID) and Iκ Bα for autosomal-dominant EDA-ID (AD-EDA-ID). Both genes are involved in NF-κB activation, such that mutations or related defects cause impaired NF-κB signaling. In particular, NEMO mutations are scattered across the entire NEMO gene in XL-EDA-ID patients, which ex- plains the broad spectrum of clinical manifestations and the difficulties associated with making a diagnosis. In this review, we focus on the pathophysiology of EDA-ID and different diagnostic strategies, which will be bene- ficial for early diagnosis and appropriate treatment. KEY WORDS anhidrotic ectodermal dysplasia with immunodeficiency, immunodeficiency, inflammation, NEMO, NF-kappaB inhibitor alpha treatment of EDA-ID, the physicians should be well INTRODUCTION aware of the broad spectrum of its clinical pheno- Anhidrotic ectodermal dysplasia with immunodefi- types. Moreover, in the genetic diagnosis of XL-EDA- ciency (EDA-ID) is a primary immunodeficiency dis- ID, the potential presence of a NEMO pseudogene order in which patients present with various manifes- and the occurrence of somatic mosaicism must be tations, such as EDA, vascular anomalies, and os- considered. In this review, we focus on the variable teopetrosis.1-5 The immunological features of EDA-ID clinical manifestations of XL-EDA-ID and the diagnos- include susceptibility to pathogens, impaired anti- tic precautions that can be taken in individuals at risk body response to polysaccharrides, hypogamma- for the disease. globulinemia, hyper IgM syndrome, impaired natural killer (NK) cell cytotoxicity, and autoimmune dis- ETIOLOGY OF EDA-ID eases.6 Two genes responsible for EDA-ID have been The first case of EDA-ID, in a boy who died of miliary identified: nuclear factor-κB(NF-κB) essential modu- tuberculosis, was reported by Frix et al. in 1986.8 The lator (NEMO) in X-linked EDA-ID (XL-EDA-ID) and second case involved a boy who suffered from multi- IκBα in autosomal-dominant EDA-ID (AD-EDA-ID). ple life-threatening infections caused by Pseudomonas Both genes are involved in NF-κB activation such aeruginosa, Mycobacterium avium, and cytomegalovi- that mutations or related defects cause impaired NF- rus infections.3 In spite of extensive searches for the κB signalling.5,7 For the appropriate diagnosis and cause of the refractory infections in these patients, 1Department of Pediatrics, Kyoto University Graduate School of Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606−8507, Japan. Medicine, Kyoto, Japan. Email: [email protected] Conflict of interest: No potential conflict of interest was disclosed. Received 21 March 2012. Correspondence: Ryuta Nishikomori, MD, PhD, Department of Pe- !2012 Japanese Society of Allergology diatrics, Kyoto University Graduate School of Medicine, 54 Allergology International Vol 61, No2, 2012 www.jsaweb.jp! 207 Kawai T et al. antigen LPS TNF-D CD40L TLR4 TNFR CD40 TCR TOLLIP MyD88 TRADD TRAF6 TRAF2 TRAF1 FADD TRAF3 IRAK TRAF2 CARMA1 BCL10 TRAF6 MALT1 RIP NEMO IKK-D IKK-E cytoplasm Phosphorylation P 㩷㩷㩷㸢polyubiquitination degradation INB INB in proteasome p50 p60 Ub p50 p60 nucleus NF-NB Fig. 1 NF-κB activation pathways associated with NEMO and IκBα. The major molecules involved in the TLR-4, TNFR, CD40, and TCR signalling pathways and NEMO-mediated NF-κB activation are depicted. TOLLIP, Toll-interacting protein; MyD, myeloid differentia- tion factor; IRAK, interleukin-1 receptor-associated kinase; TRAF, tumor necrosis factor re- ceptor-associated factor; TRADD, tumor necrosis factor receptor-associated death domain; FADD, fas-associated protein with death domain; RIP, receptor-interacting protein; CARMA, caspase recruitment domain-containing membrane-associated guanylate kinase protein; BCL, B-cell lymphoma protein; MALT, mucosa-associated lymphoid tissue lympho- ma translocation protein; Ub, poly-ubiquitin chain; P, phosphate. immunological dysfunctions were not identified. In mated incidence of XL-EDA-ID is 1 : 250,000 live male 1996, Abinun et al. described a young male patient births.6 In AD-EDA-ID, six patients and four IκBα with EDA-ID who had an impaired antibody response mutations have been reported thus far.7,12-15 to polysaccharide antigens.2 Their report was the first THE ROLES OF NEMO AND Iκ Bα IN THE to shed light on the mechanism of EDA-ID-associated κ immunodeficiency. In 2001, three groups were able NF- B ACTIVATION PATHWAY to show that defects in the NEMO gene are responsi- NF-κB transcription factors are critical regulators of ble for XL-EDA-ID. Those authors demonstrated that immunity, the stress response, apoptosis, and differ- the clinical manifestations of XL-EDA-ID, including entiation. Mammalian cells make use of two main NF- EDA and the immunological dysfunctions, were κB activation pathways, the canonical pathway and caused by impaired NF-κB activation due to the iden- the non-canonical pathway. The canonical pathway, in tified genetic alterations.5,9,10 In addition, in a 2003 pa- which NEMO and inhibitors of NF-κB(IκB) are es- per by Courtois et al., the etiology of AD-EDA-ID was sential control elements, is induced by most physi- determined to be a heterozygous gain-of-function mu- ological NF-κB stimuli.16 NEMO and IκBarealsoin- tation in the IκBα gene.7 As both forms of EDA-ID volved in the non-canonical NF-κB activation path- are typically diagnosed by genetic testing, NEMO way, albeit indirectly.17 Homo- or heterodimers of and IκBα mutations have been linked to a broad NF-κB proteins (p50, p52, RelB, and c-rel) are nor- spectrum of clinical phenotypes.11 Currently, the esti- mally retained in the cytoplasm through interactions 208 Allergology International Vol 61, No2, 2012 www.jsaweb.jp! Manifestations and Mutations in EDA-ID A NEMO gene exon 1d 1a 1b 1c 2 3 4 5 6 7 8 9 10 NEMO pseudogene B D311E D311N E315A L80P L153R R173G R217G R254G E319Q E391X D406VC417R,F,Y D113N A169P R175P R182P L227P A288G E331del3 Q403X Q348X 419 NH21 CC1 CC2 NUB LZ ZF COOH Id Ia Ib Ic II III IV V VI VII VIII IX X 5’ 1 1257 3’ +1 of the donor splice site of 769(-1)G 1056(-1)G>A exon1B G>T >C (del 353-373) 110_111insC(49X) Ex4_6del Ex4_6dup 811_28del 1166_78dup(398X) (233X) (del 271-276) 1161_67insC(394X) 1218insC(419X) 1235insC(419X) X420Wro(447X) C Serine 32 Serine 36 72 277 317 Phosphorylation NH2 Ankyrin Repeat Domains PSET COOH sites Q9X W11X E14X S32I Fig. 2 Schematic representations of the normal NEMO and IκBα genes. (A) The normal NEMO gene and a NEMO pseudo- gene. Schematic representation of the coding-region domain and reported mutations in NEMO (B) and IκBα (C). with IκB family proteins, which consist of IκBα,IκBβ, The human NEMO gene, located at Xq28, is a 23-kb and IκBε. In response to the appropriate signals, gene structured in nine exons and four alternative these three proteins are phosphorylated, polyubiquiti- non-coding first exons. A non-functional copy of the nated, and degraded though the ubiquitin-protea- NEMO gene, IKBKGP (also referred to as the some pathway (Fig. 1), thereby freeing NF-κBto NEMO pseudogene), is located 31.6 kb distal to exon translocate to the nucleus where it activates its target 10 (Fig. 2A). IKBKGP maps within a 35.7-kb dupli- genes.16 cated fragment that is oriented tail to tail with the The phosphorylation event in this sequence is car- NEMO gene and contains exons 3-10, with 99.8% ho- ried out by a high molecular mass, multiprotein mology.18 The ~48-kDa NEMO protein is composed kinase complex containing two subunits with kinase of two coiled coil (CC1, CC2) domains, a leucine- activity (IKK1!α and IKK2!β) and NEMO (IKK3!γ). zipper (LZ) domain, a NEMO ubiquitin-binding Allergology International Vol 61, No2, 2012 www.jsaweb.jp! 209 Kawai T et al. Table 1 Clinical and immune function associated with hypomorphic NEMO mutations in reported cases and Japanese cases Functional or clinical category Modifi ed - Hanson et al.11 Japanese cases Ectodermal dysplasia 40/52 ( 77%) 9/10 ( 90%) Osteopetrosis 5/65 ( 8%) 0/10 ( 0%) Lymphedema 5/65 ( 8%) 1/10 ( 10%) Autoimmune/infl ammatory disease 14/66 ( 23%) 5/10 ( 50%) Dead 24/66 ( 36%) 2/10 ( 20%) Infectious susceptibility 60/61 ( 98%) 10/10 (100%) Bacterial infection 45/52 ( 86%) 10/10 (100%) Mycobacterial infection 23/52 ( 44%) 4/10 ( 40%) Pneumocystis pneumonia 4/52 ( 21%) 0/10 ( 0%) DNA-virus infection 11/52 ( 21%) 1/10 ( 10%) Meningitis 12/61 ( 21%) 1/10 ( 10%) Pneumonia 19/61 ( 31%) 3/10 ( 30%) Sepsis/bacteremia 20/61 ( 33%) 5/10 ( 50%) Abscess 18/61 ( 30%) 3/10 ( 30%) Hypogammaglobulinemia 24/41 ( 59%) N.D. Specifi c antibody defi ciency 18/28 ( 64%) N.D. Impaired antibody response to polysaccharide 13/16 ( 94%) 3/3 (100%) Impaired NK cell cytotoxicity 10/10 (100%) N.D. (NUB) domain, and a zinc finger (ZF) domain (Fig. while phosphorylation of Ser32 and Ser36 in its phos- 2B).19 NEMO has no apparent catalytic activity but is phorylation domains triggers IκBα ubiquitination, instead required in activation of the kinase complex leading to degradation of the protein within the pro- in response to extracellular (or intracellular) stimuli, teasome and, in turn, the nuclear translocation of NF- such as members of the TIR (TLR-ligands, IL-1β,and κB and subsequent activation of its target genes.