The immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome (IPEX) is a rare and severe disorder characterized by autoimmune enteropathy, early-onset type 1 diabetes mellitus, thyroiditis, and eczema. It usually develops in neonates and is often fatal. It is caused by mutations of the FOXP3 gene (1,2). This gene encodes a DNA-binding protein (FOXP3) that is essential for the induction and maintenance of peripheral immune tolerance in the tissues through its role as the key transcription factor required for differentiation and activation of CD4+CD25+ regulatory T lymphocytes. A deficiency of these cells causes increased immunologic reactivity and autoimmunity (3).
Autoimmune hepatitis (AIH) is divided into 2 subtypes according to seropositivity for smooth muscle and/or anti-nuclear antibody (SMA/ANA, type 1) or liver kidney microsomal antibody (LKM1, type 2) (4). Type 2 AIH is rare. LKM1-positive patients tend to present with more fulminant disease at a younger age. Acute liver failure is a frequent form of presentation (5,6). We present the case of a male child with AIH type 2 in whom IPEX syndrome was diagnosed and confirmed by mutation analysis of the FOXP3 gene.
The patient is a 4-year-old boy, born at term with a birth weight of 2700 g after an uneventful pregnancy. The parents were nonconsanguineous and the boy had a healthy sister and brother. His father developed Hodgkin lymphoma in his 20s and is currently in remission. The patient was exclusively breast-fed during the first 3 months of life. His immunizations were complete and well tolerated. At 2 months of age, he developed atopic eczema and had frequent superinfections.
Growth was normal up to 2 years of life, when the child presented with chronic diarrhea, greasy and pale stools, malnutrition, and failure to thrive. He was hospitalized on several occasions because of dehydration. Celiac disease was diagnosed at 4 years of age based on the finding of villous atrophy of the small bowel, after ruling out parasitic and bacterial etiology and cystic fibrosis. He was placed on a gluten-free diet and parenteral nutrition but was referred to our hospital 2 months later because of a lack of response to the diet, chronic diarrhea, and severe malnourishment.
On admission, physical examination showed a severely malnourished boy with a weight of 10.5 kg (z score −3.5), a height of 99 cm (z score −1.3), and normal head circumference. Laboratory findings showed mild iron-deficiency anemia; 24-hour fecal fat excretion was 3 g (normal value [NV] <2 g/24 hours) and alpha-1-antitrypsin clearance was 71 mg/24 hours (NV <20 mg/24 hours). Anti-tissue transglutaminase antibodies were negative; immunoglobulin (Ig) A levels, liver function, and fecal level of elastase were within normal ranges. Stool culture, screening for ova and parasites, and mutational tests for cystic fibrosis were negative. Gastrointestinal transit was normal. Although endoscopic appearance of the gastrointestinal tract was normal, small-bowel biopsy was repeated showing severe patchy villous atrophy with a mononuclear cell infiltrate (activated T cells) in the lamina propria without increased intraepithelial lymphocytes. The patient continued on the gluten-free diet and semielemental nutrition, which led to clinical improvement and weight gain. He was discharged 2 months after admission with a weight of 13.2 kg (z score −2.32).
At a follow-up visit 2 months later, the patient was found to have hepatomegaly. Laboratory findings showed hypereosinophilia, severe elevation of transaminase levels (aspartate aminotransferase 1339 IU/L [NV ≤48 IU/L], alanine aminotransferase 2153 IU/L [NV ≤38 IU/L]), and elevated serum Ig: IgG 2200 mg/dL (NV 664–1176 mg/dL), IgM 193 mg/dL (NV 38–74 mg/dL), and IgE 46 IU/mL (NV ≤15 IU/mL). IgA levels were within normal limits (92 mg/dL, NV 66–120 mg/dL).
Serologic tests for hepatitis A, B, and C viruses, Epstein-Barr virus, cytomegalovirus, and human immunodeficiency virus were negative. Metabolic disorders were excluded. There was no history of drug ingestion.
Non–organ-specific autoantibodies were tested by indirect immunofluorescence technique and the LKM1 antibody was found to be strongly positive with a titer of 1:3000 (dilution techniques according to our laboratory). Anti-nuclear and anti-smooth muscle antibody tests were negative. No family history of autoimmune disorders or liver disease was found. Human leukocyte antigens (HLAs) were determined using PCR-SSO (LABType, One Lambda Canoga Park, CA) with the following result: HLA-DRB*04. Liver synthetic function deteriorated in the course of that week (international normalized prothrombin ratio 1.44 [NV 0.9–1.2]). Glucose levels remained within normal limits. Based on clinical and laboratory findings, AIH type 2 was suspected. According to the International Autoimmune Hepatitis Group criteria (4), the boy was diagnosed with probable AIH (score 13, in the supplementary table, http://links.lww.com/MPG/A54). He was begun on immunosuppressive therapy with 2 mg · kg−1 · day−1 prednisone, leading to rapid improvement of liver function. Liver biopsy was performed 20 days later when the international normalized prothrombin ratio normalized. This showed an inflammatory infiltrate containing lymphoplasmacytic cells in the portal tract, invading the lobule, and producing interface hepatitis compatible with AIH (histologic activity index 10/18, stage 3/6) (Figs. 1 and 2). The definitive diagnosis of AIH was made (score after biopsy and therapy 20, in the supplementary table, http://links.lww.com/MPG/A54). Because liver function recovered and transaminases decreased, the prednisone dose was reduced.
Forty days after initiation of prednisone treatment, while he was on a dose of 0.8 mg · kg−1 · day−1, the patient was again admitted to the hospital but this time for severe diabetic ketoacidosis. Type 1 diabetes mellitus was diagnosed and insulin treatment was begun. Anti-islet cell cytoplasmic autoantibodies and glutamic acid decarboxylase antibodies were negative. Steroids were discontinued to avoid adverse effects and cyclosporine microemulsion was started. Liver aminotransferase levels declined gradually and AIH remitted 3 months after diagnosis. Cyclosporine was switched to a combination of low-dose prednisone and azathioprine.
Based on the clinical picture of a boy with atopic eczema, enteropathy, AIH, and diabetes mellitus, IPEX syndrome was suspected. Immunologic studies showed high IgG, IgM, and IgE and decreased CD4+CD25+FOXP3+ lymphocytes (patient 0.03% of CD4+ T cells vs control 4.4%). Molecular analysis confirmed a 3-base pair in-frame deletion mutation in the leucine zipper of FOXP3 (c.748-750delAAG) that causes deletion of a single lysine at position 250 (p.250K.del), a mutation previously described in IPEX syndrome (3) and sometimes associated with a somewhat milder disease phenotype. Sequence analysis of the mother was normal.
At 6 years of age, the patient was again placed on a gluten-containing diet because his disease process was believed to be primarily an autoimmune enteropathy rather than celiac disease. Thyroid disease was ruled out, thyroid-stimulating hormone levels were always normal, and autoantibodies to thyroid antigens were repeatedly negative. Following the change of immunosuppression from steroids to cyclosporine microemulsion, the diabetes improved and the insulin requirements resolved. Liver function tests remained normal under treatment with low-dose prednisone and azathioprine. Anti-LKM1 antibodies became negative. The patient underwent bone marrow transplantation from his HLA-matched brother 15 months after the diagnosis of IPEX syndrome and has clinically improved.
IPEX is a primary immunodeficiency disease of immune dysregulation. It shares features with other syndromes associated with autoimmunity such as autoimmune lymphoproliferative syndrome and autoimmune polyendocrinopathy with candidiasis and ectodermal dystrophy. Clinical manifestations, gene defects, and pathogenesis allow differentiation between these entities (7).
IPEX is a rare disorder that usually develops in neonates and is often fatal. It presents most commonly in the first few months of life with dermatitis, mostly manifested by eczema. Severe watery diarrhea caused by autoimmune enteropathy is almost universal and leads to cachexia and growth retardation (8). Bowel biopsies typically show significant villous atrophy and chronic inflammation with excessive cytokine production (9). Early onset of type 1 diabetes mellitus and autoimmune thyroid disease also are common. The treatment of IPEX typically involves the use of aggressive immunosuppression and bone marrow transplantation, which may be curative, even in the setting of mixed chimerism in the recipient (10–12).
IPEX is caused by mutations in the FOXP3 gene. The particular mutation identified in our patient (p.250K.del) has been described in association with IPEX (3,13) and is frequently associated with a somewhat milder disease phenotype (T.R. Torgerson, unpublished data), although, as demonstrated by this patient, severe autoimmunity remains a problem. Other mutations associated with a milder phenotype and prolonged survival have been described, with some affected boys surviving from 7 to 24 years without bone marrow transplantation (14–16).
Our patient met the diagnostic criteria for AIH of the International Autoimmune Hepatitis Group (4). The pathogenic mechanisms that initiate the generation of autoantibodies and liver cell destruction in AIH are as yet unknown, despite extensive investigation into both humoral and cell-mediated adaptive immunity (6). It is known, however, that the process of autoantigen recognition is strictly controlled by regulatory mechanisms that, if failing, permit the autoimmune attack (17).
In IPEX, the development of AIH is almost certainly related to the general predisposition for organ-specific autoimmunity caused by the absence of functional CD4+CD25+FOXP3+ regulatory T cells. Recent data have suggested that patients with IPEX have a remarkable predisposition to develop autoantibodies against a host of different autoantigens (18–20). The spectrum of autoantibodies is broad and has been reported to target a variety of antigens expressed in the skin, gut, kidneys, pancreas, and on various hematopoietic cells (9). Some of them appear to contribute to disease pathogenesis. Tsuda et al (20) performed autoantibody screening in serum samples from patients with the diagnosis of IPEX syndrome, confirmed by sequencing of the FOXP3 gene, and identified a broad spectrum of autoantibodies (anti-nuclear, anti-mitochondrial, anti-tTG autoantibodies) to extractable nuclear antigens and against centromere antigens. Interestingly, there does not seem to be a particular pattern of autoantibodies associated with IPEX. This is the first report, to our knowledge, of a patient with IPEX developing anti-LKM1 antibodies.
The presentation and evolution of our patient were somewhat milder than those observed in classic IPEX with regard to both the age at presentation and the spontaneous improvement of enteropathy and diabetes. In spite of this, the patient had persistent and significant failure to thrive and was by no means clinically normal; however, the patient improved after bone marrow transplantation. Hepatitis and hepatomegaly have been described in IPEX, including in 1 patient with the same mutation who had hepatomegaly and mild hepatitis with focal hepatosteatosis on liver biopsy (2), but to our knowledge, this is the first report of a patient with IPEX developing type 2 AIH.
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