A recent review (S Chandrakasan, S Venkateswaran, S Kugathasan [corrresponding author]. Pediatr Clin N Am 2017; 64: 139-160) provides a surprisingly easy read on very early onset (VEO) inflammatory bowel disease (IBD) (Thanks to Kathleen McNamara for sharing). Because of the myriad of genetic defects (>50 monogenetic defects), the topic of VEO-IBD can be quite confusing. The authors of this summary make a number of key points.
- VEO-IBD is increasing in incidence
- Many patients with VEO-IBD have an underlying primary immune defect. Identification of these underlying disorders may allow targeted therapy.
- In some patients, hematopoietic stem cell transplantation could result in definitive cure
- VEO features: more often involves colon and often severe course with poor response to conventional immunosuppressives
Besides idiopathic IBD, the differential can be subdivided into subgroups:
- T-cell defects (IPEX and IPEX-like) (gene defects: FOXP3, LRBA CTLA4, STAT1, STAT3, STAT5B, CD25, CTLA4, )
- Defects in IL-10 signaling (IL10RA, IL10RB, IL-10)
- Hyperinflammtory/autoinflammatory disorders (XIAP/SAP (BIRC4), Mevalonate kinase deficiency (MVK), PLCG2, Familial Mediterranean Fever, Familial HLH Type 5: STXBP2, Hermansky-Pudlak: HPS1, HPS4, HPS6)
- Defects in neutrophil function/phagoycte function (chronic granulomatous disease (CGD) genes: CYBB, CYBA, NCF1, NCF2, NCF4,, Leukocyte Adhesion Defect (LAD) ITGB2, GSD type 1bSLC37A4, congenital neutropenia G6PC3)
- Epithelial barrier defect (X-linked ectodermal dysplasia and immunodeficiency (NEMO), TTC7A, ADAM17, dystrophic epidermolysis bullosa (COL7a1), Kindler syndrome (FERMT1), mutations in guanylate cyclase c, telomere biology defects like DKC and RTEL1 )
- T/B cell defects (X-linked agammaglobulin (BTK), SCID/Omenn (RAG1, RAG2, IL-7Ra, IL-2RG), CVID, IL21, Wiskott-Aldrich (WAS) HIES, HIMS)
The authors provide some vignettes of a typical presentation of each subset along with some commentary. For example, with T-cell defects: “mutations in FOXP3 result in either absent or decreased Treg cell numbers or a qualitative defect…results in broader immune dysregulation, resulting in multisystem autoimmunity with autoimmune endocrinopathy, autoimmune cytopenia, autoimmune hepatitis, and severe eczema.” Other IPEX-like mutations include gain of function in STAT-1/STAT-3, LRBA deficiency, and CTLA-4 haploinsufficiency.
The authors recommend an initial immune evaluation in VEO-IBD:
- peripheral smear evaluation
- immunoglobulin levels, lymphocyte subsets with T-cell
- B-cell, and NK-cell enumeration
- CD45RA/RO enumeration and B-cell panel for class-switched memory B cells
- neutrophil oxidative burst
- T regulatory cell (CD4+CD25+FOXP3+) cell enumeration.
Due to the increasing complexity of the immune evaluation, the necessity of a pediatric immunologist is apparent. In addition, the role of genetic panels that test for all of these disorders simultaneously is becoming routine. Genetic testing can help improve diagnosis and allow for early targeted intervention. With the emergence of new defects, selecting the right lab with an up-to-date panel is another caveat.
Examples of targeted therapies include the potential role of anakinra for CGD, abatacept for LRBA deficiency, toclizumab (IL-6 receptor blocking antibody) for STAT3 gain-of-function mutation, and sirolimus for Treg disorders. Hematopoietic stem cell transplantation is an established therapy for IL-10 signaling defects.
My take: Collaboration with immunology is an important consideration in young children with IBD.
Related blog posts:
- Expanding VEO Variants
- Just the Beginning: Mutations in Very Early Onset … – gutsandgrowth
- Exome Sequencing in VEO-IBD: More Data | gutsandgrowth
Disclaimer: These blog posts are for educational purposes only. Specific dosing of medications (along with potential adverse effects) should be confirmed by prescribing physician. This content is not a substitute for medical advice, diagnosis or treatment provided by a qualified healthcare provider. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a condition.