Bone Marrow Failure and Immunodeficiency Associated with Human RAD50 Variants.

PURPOSE: The MRE11-RAD50-NBN (MRN) complex plays a key role in recognizing and signaling DNA double-strand breaks. Pathogenic variants in NBN and MRE11 give rise to the autosomal-recessive diseases, Nijmegen breakage syndrome (NBS) and ataxia telangiectasia-like disorder, respectively. The clinical consequences of pathogenic variants in RAD50 are incompletely understood. We aimed to characterize a newly identified RAD50 deficiency/NBS-like disorder (NBSLD) patient with bone marrow failure and immunodeficiency. METHODS: We report on a girl with microcephaly, mental retardation, bird-like face, short stature, bone marrow failure and B-cell immunodeficiency. We searched for candidate gene by whole-exome sequencing and analyzed the cellular phenotype of patient-derived fibroblasts using immunoblotting, radiation sensitivity assays and lentiviral complementation experiments. RESULTS: Compound heterozygosity for two variants in the RAD50 gene (p.Arg83His and p.Glu485Ter) was identified in this patient. The expression of RAD50 protein and MRN complex formation was maintained in the cells derived from this patient. DNA damage-induced activation of the ATM kinase was markedly decreased, which was restored by the expression of wild-type (WT) RAD50. Radiosensitivity appeared inconspicuous in the patient-derived cell line as assessed by colony formation assay. The RAD50R83H missense substitution did not rescue the mitotic defect in complementation experiments using RAD50-deficient fibroblasts, whereas RAD50WT did. The RAD50E485X nonsense variant was associated with in-frame skipping of exon 10 (p.Glu485_545del). CONCLUSION: These findings indicate important roles of RAD50 in human bone marrow and immune cells. RAD50 deficiency/NBSLD can manifest as a distinct inborn error of immunity characterized by bone marrow failure and B-cell immunodeficiency.

Pirarubicin Combination Low-Dose Chemotherapy for Early Infantile Stage MS Neuroblastoma: Case Report.

Neuroblastoma (NB) is a neural crest-derived malignant tumor which is diagnosed during infancy in approximately 40% of cases; spontaneous regressions are observed, but there are varying degrees of severity. Treatment is indicated if an infant's condition is at risk of deterioration. Herein, we report the case of a 42-day-old boy who presented with hepatomegaly and was diagnosed with stage MS NB. A pathological diagnosis of "poorly differentiated neuroblastoma with low mitosis-karyorrhexis index, favorable histology" was made; his tumor cells were hyperdiploid and MYCN was not amplified. Because he had respiratory distress caused by the rapidly evolving hepatomegaly, two cycles of chemotherapy containing vincristine and cyclophosphamide were administered in the second and fourth weeks of admission; however, his abdominal tumor did not shrink. In the sixth week of admission, chemotherapy was revised to pirarubicin and cyclophosphamide, and the tumor began to shrink. After discharge, there was no re-elevation of tumor markers; after 1 year, the hepatomegaly and liver metastases disappeared. During the 5-year follow-up, his growth and development were normal and he progressed without sequelae. A regimen that includes pirarubicin could merit further study in the treatment of early infants with stage MS low-risk NB who are at risk of complications.

Prognostic Factors for Outcomes of Allogeneic HSCT for Children and Adolescents/Young Adults With CML in the TKI Era.

The breakthrough effects of tyrosine kinase inhibitors (TKIs) have lessened indications for allogeneic hematopoietic stem cell transplantation (HSCT) in chronic myeloid leukemia (CML). However, HSCT is still attractive for children and adolescents/young adults (AYAs) requiring lifelong TKI therapy. Nevertheless, little has been reported on the outcomes of large clinical studies of HSCT targeting these age groups. This study aimed to identify prognostic factors for the outcomes of HSCT, including reduced-intensity conditioning (RIC)-HSCT, for children and AYAs with CML in the TKI era. We performed a registry analysis for 200 patients with CML aged <30 years who underwent pretransplant TKI therapy from the observational nationwide database established by the Japanese Society for Transplantation and Cellular Therapy. The patients received bone marrow (BM), peripheral blood (PB), or cord blood (CB) from either related or unrelated donors. The indication for HSCT for individual patients was determined by the institution according to European LeukemiaNet recommendations and other guidelines. The 5-year overall survival (OS) rates for patients with chronic phase (CP) (n = 124), accelerated phase (AP) (n = 23), and blastic phase (BP) (n = 53) at diagnosis were 82.8%, 71.1%, and 73.3%, respectively, with no significant difference (P =.3293). The strongest predictor of engraftment was transplant source, with CB (hazard ratio [HR], 0.33) and PB (HR, 2.00) (compared with BM) being independent unfavorable and favorable predictors, respectively. Transplant source was also an independent predictor of chronic GVHD, with PB (HR, 1.81) and CB (HR, 0.39) (compared with BM) being unfavorable and favorable predictors, respectively. The strongest predictor of OS rate for patients with CP at diagnosis was disease phase at HSCT, with second or greater CP, AP, or BP (HR, 2.81) (compared with first CP [CP1]) being an unfavorable predictor. In addition, patients with CP at diagnosis who had major and complete molecular responses at HSCT had excellent outcomes, with 5-year OS rates of 100% and 94.4%, respectively. The 5-year OS rate was compared between RIC (n = 31) and myeloablative conditioning (MAC) (n = 58) in patients with CP1, both of which were 89.3%, with no significant difference (P = .9440). On univariate analysis for the RIC cohort with CP at diagnosis, the age at HSCT (HR, 1.27) (increase per year) and the time from diagnosis to HSCT (HR, 1.83) (increase per year) were significant predictors for OS. Our study demonstrates that RIC may be an appropriate alternative to MAC for children and AYAs with CP1. As for the transplant source, we recommend first selecting BM because of a higher engraftment rate compared to CB and a lower incidence of chronic GVHD compared to PB. Although HSCT in the status of a major molecular response is desirable, it is not advisable to continue TKI pointlessly long because age at HSCT and timing of HSCT are prognostic factors that determine survival. The decision to perform RIC-HSCT instead of continuing TKI should be carefully made, considering the possibility of transplant-related complications.

Characterization of PD-1/PD-L1 immune checkpoint expression in the pathogenesis of musculoskeletal Langerhans cell histiocytosis: A retrospective study.

ABSTRACT: Recent data suggest that programmed cell death -1 (PD-1) and programmed cell death ligand-1 (PD-L1) are involved in the pathogenesis of Langerhans cell histiocytoma (LCH); however, their contributions are not well established. Also, the involvement of PD-1/PD-L1 molecules in musculoskeletal LCH remains particularly unclear. The current study aims to characterize the involvement of PD-1/PD-L1 immune checkpoint system in the pathogenesis of musculoskeletal LCH. PD-1/PD-L1 expression was evaluated in 6 patients, 3 men and 3 women with a mean age of 13.5 years, with musculoskeletal LCH who were treated at Kindai University Hospital and Osaka Women's and Children's Hospital between November 2005 and December 2020. The median follow-up period for all patients with musculoskeletal LCH was 41 months. We surveyed symptoms, number of lesions, treatment modality, and outcomes. Immunostaining for CD4, CD8, PD-1, and PD-L1 was also performed on pathological specimens obtained by biopsy. Multiple lesions were observed in 5 cases, and a single lesion was observed in 1 case. The chief complaint in 5 cases was pain. Four patients underwent spontaneous regression. The other 2 patients received chemotherapy. The outcomes included continuous disease-free (n = 5) and alive with the disease (n = 1). The CD4-, CD8-, PD-1-, and PD-L1-positive rates among all specimens were 100%, 100%, 16.6%, and 83.3%, respectively. The CD4/PD-L1, CD8/PD-L1, and PD-1/PD-L1 positive rates in all the specimens were 83.3%, 83.3%, and 16.6%, respectively. We believe that the PD-1/PD-L1 immune checkpoint molecules may play some role in the microenvironment of musculoskeletal LCH.

Treatment Outcomes of Langerhans Cell Histiocytosis: A Retrospective Study.

Background and Objectives: Langerhans cell histiocytosis (LCH) is a rare disease characterized by the infiltration of one or more organs by Langerhans cell-like dendritic cells. LCH often involves the bone, and its clinical evidence is limited. The purpose of this study is to report on the treatment of LCH at our institution and to add to the evidence for LCH. Materials and Methods: We reviewed six cases of LCH treated in our hospital between November 2005 and February 2016. Patient age at the first visit, sex, site of origin, symptoms, image tools used for diagnosis, biopsy site, complications, treatment, and final clinical outcome were evaluated. The median follow-up period was 41 months. Results: The median patient age at the first visit was 13.5 years. Three male and three female individuals were enrolled. Multiple lesions were observed in five cases, and a solitary lesion was observed in one case. Pain was the chief complaint in five cases. Radiography was the most commonly used imaging tool. Bone scintigraphy or magnetic resonance imaging and positron emission tomography-computed tomography were also used to diagnose systematic LCH. Biopsy of the femur was performed in two cases, and biopsy of the tibia, lumbar vertebrae, rib, and radius was performed in one case each. Regarding comorbidities, one case of hepatitis B and one case of autism were observed. Chemotherapy was initiated in two patients. The other four patients were observed naturally. Continuous disease-free survival was observed in five patients. One patient remained alive but not without disease during the final follow-up examination. Conclusion: LCH should be diagnosed as early as possible to treat it appropriately.

Donor-derived myelodysplastic syndrome after allogeneic stem cell transplantation in a family with germline GATA2 mutation.

Germline GATA2 heterozygous mutations were identified as complex immunodeficiency and hematological syndromes characterized by cytopenia (monocytes, B-cells, NK-cells), susceptibility to mycobacterium, fungus, or Epstein-Barr virus (EBV) infection, and myelodysplastic syndrome (MDS)/acute myelogenous leukemia (AML) development. Herein, we report a patient with AML who had a fatal infection after allogeneic hematopoietic stem cell transplantation (HSCT) due to impaired immune reconstitution associated with GATA2 mutation. A 15-year-old man was diagnosed with AML with monosomy 7. His family history was negative for immunodeficiency and hematological disorders. He attained complete remission after HSCT from an HLA-identical sister. Post-HSCT examinations performed 15 months later revealed pancytopenia, especially monocytopenia and the absence of B and NK cells, resulting in the occurrence of donor-type MDS. Twenty-one months after HSCT, he developed central nervous system aspergillosis and finally died of the disease. Two months later (24 months after PBSCT), the donor was diagnosed with persistent EBV infection accompanied by MDS with multilineage dysplasia. Genetic analysis of GATA2 revealed a novel heterozygous mutation (c.1023_1026dupCGCC) in both siblings. GATA2 mutations were highly prevalent among adolescent MDS/AML patients with monosomy 7. Therefore, the screening of GATA2 mutations in relatives is necessary when performing HSCT from a relative donor.

Prevalence of germline GATA2 and SAMD9/9L variants in paediatric haematological disorders with monosomy 7.

Monosomy 7 (-7) occurs in various types of paediatric myeloid disorders and has a poor prognosis. Recent studies have demonstrated that patients with germline gain-of-function SAMD9/9L variants and loss-of-function GATA2 variants are prone to developing myelodysplastic syndrome (MDS) associated with -7. However, the prevalence of the genetic variants among paediatric haematologic disorders with -7 is unknown. The present study screened germline variants of GATA2 and SAMD9/9L in 25 patients with various types of paediatric haematological disorders associated with -7. The diagnoses of the 25 patients included MDS (n = 10), acute myeloid leukaemia (AML) and myeloid sarcomas (n = 9), juvenile myelomonocytic leukaemia (n = 3) and other disorders (n = 3). Seven patients with a germline pathogenic GATA2 variant were found. For SAMD9/9L screening, next-generation sequencing was used to detect low-abundance variants and found four novel germline variants. Functional analysis revealed that three out of the four variants showed growth-restricting capacity in vitro and thus, were judged to be pathogenic. Cases with GATA2 mutation tended to be older, compared to those with SAMD9/9L mutations. In conclusion, GATA2 and SAMD9/9L were sequenced in 25 patients with paediatric haematologic disorders associated with -7, and 40% of them were found to have some pathogenic germline variants in the three genes.

An 18-Year-Old Male With X-linked Lymphoproliferative Syndrome Type 1 Who Developed Primary Central Nervous System Lymphoma 6 Months After Primary Epstein-Barr Virus Infection.

X-linked lymphoproliferative syndrome type 1 (XLP1) is a rare congenital immunodeficiency disease. We report the case of an 18-year-old male who developed hemophagocytic lymphohistiocytosis (HLH) with neurologic complications after primary Epstein-Barr virus (EBV) infection and subsequently developed EBV-related central nervous system lymphoma (CNSL). Given the vulnerability to EBV, he was finally diagnosed with XLP1 and treated with whole-brain irradiation along with chemotherapy and subsequent allogeneic hematopoietic stem cell transplantation from a SH2D1A wild-type sibling donor. Although the prognosis for CNSL is generally dismal, reconstitution of the immune system from a normal donor contributed to the patient remaining in remission for 30 months.

Impact of sirolimus treatment for refractory kaposiform hemangioendothelioma with exacerbation of the disease 10 years after initial diagnosis.

We describe our experience with a 12 year-old girl with kaposiform hemangioendothelioma accompanied by Kasabach-Merritt phenomenon with exacerbation of the disease 10 years after the initial diagnosis. Kaposiform hemangioendothelioma infiltrated into the subcutaneous tissue of the facial skin with deterioration of coagulopathy despite conventional therapies including corticosteroid, vincristine, and propranolol. Sirolimus, a mammalian target of rapamycin inhibitor, produced rapid and dramatic improvement of the Kasabach-Merritt phenomenon and kaposiform hemangioendothelioma shrinkage. Eventually, multifocal lesions of kaposiform hemangioendothelioma disappeared on the images of magnetic resonance imaging and have remained in remission for 27 months after sirolimus cessation. We demonstrated that the AKT/mammalian target of rapamycin signaling pathway played a pivotal role in the kaposiform hemangioendothelioma growth. Sirolimus must be a strong candidate for molecular therapy targeting kaposiform hemangioendothelioma.

Successful Treatment of Transplantation-associated Atypical Hemolytic Uremic Syndrome With Eculizumab.

We herein reported a 4-month-old boy with transplantation-associated atypical hemolytic uremic syndrome (TA-aHUS) who was successfully treated with eculizumab. The patient diagnosed with type 3 of familial hemophagocytic lymphohistiocytosis underwent cord blood transplantation. After transplantation, he developed TA-aHUS, but plasma exchanges were unsuccessful. We identified deletions in CFH-related gene 1 (del-CFHR1) by the multiplex ligation-dependent probe amplification testing procedure and CFH autoantibodies. Eculizumab has been administered to the patient, with a marked improvement being achieved in thrombocytopenia. He has been well except for the persistent microhematuria for a year after transplantation. Uncontrolled complement activation might be involved in the pathophysiology of TA-aHUS.

Copper-Catalyzed Regio- and Stereoselective Iodocyanation and Dicyanation of Alkynes with Cyanogen Iodide.

anti-Selective iodocyanation and dicyanation of various internal alkynes has been developed by means of a simple copper catalyst system. The selectivity of the products was switched by tuning the reaction conditions. Mechanistic studies have revealed all of the stepwise pathways including diiodide formation, selective monocyanation, and second cyanation processes.

Liver fibrosis with hypereosinophilia causing transient abnormal myelopoiesis.

Transient abnormal myelopoesis is mostly self-resolving and has a good prognosis, but some patients subsequently die of liver fibrosis. We report the case of an infant with Down syndrome who developed life-threatening liver fibrosis at the same time as the blasts were about to disappear. This patient also had a marked increase in eosinophils, which were possibly harboring a GATA1 mutation and were expressing a high level of platelet-derived growth factor-B mRNA; these may have been involved in the development of liver fibrosis. Low-dose cytosine arabinoside therapy effectively treated both hypereosinophilia and liver fibrosis.

Effects of the Cessation of Mass Screening for Neuroblastoma at 6 Months of Age: A Population-Based Study in Osaka, Japan.

BACKGROUND: In 2004, the Japanese government halted the 6-month mass screening program for neuroblastoma. We investigated whether its cessation had led to an increase not only in mortality due to this disease but also in the incidence of advanced-stage disease among older children. METHODS: Study subjects were neuroblastoma patients retrieved from the population-based Osaka Cancer Registry. Trends of incidence and mortality from neuroblastoma were analyzed by calendar year and birth cohort. Prognostic factors, including stage and v-myc avian myelocytomatosis viral oncogene neuroblastoma derived homolog (MYCN) oncogene status, were compared before and after the cessation of mass screening. RESULTS: Age-standardized incidence rates in 2005-2009 (the cessation period of mass screening; 11.1 per million) were similar to those in 1975-1979 (the pre-screening period; 8.6 per million). Age-standardized mortality rates tended to decrease from 1975-1979 (4.0 per million) to 2005-2009 (2.7 per million) in parallel with the improvement in survival. Analysis by birth cohort indicated that the mortality rates in 2004-2005 (after cessation) for children 0-4 years of age were lower than those in 1975-1979 (O:E ratio 0.25; 95% confidence interval, 0.03-0.90). For children 1-9 years of age, there was a not significant difference in the distribution of stage, MYCN oncogene status, and DNA ploidy between 1991-2003 (the mass screening period) and 2004-2008 (after cessation). CONCLUSIONS: The cessation of mass screening for neuroblastoma does not appear to have increased mortality due to this disease or incidence of advanced-stage disease among older children.

Copper-Catalyzed Cyanation of Aryl- and Alkenylboronic Reagents with Cyanogen Iodide.

Direct catalytic cyanation of organoboronic acids with cyanogen iodide has been achieved by using a copper-bipyridine catalyst system. The cyanation reaction is likely to occur through two catalytic cycles: copper(II)-catalyzed iodination of organoboronic acids and the following cyanidocopper(I)-mediated cyanation of organic iodides.

Comparison of continuous and twice-daily infusions of cyclosporine A for graft-versus-host-disease prophylaxis in pediatric hematopoietic stem cell transplantation.

BACKGROUND: Cyclosporine A (CsA) is used widely for graft-versus-host disease (GVHD) prophylaxis in hematopoietic stem cell transplantation (HSCT); however, the optimal schedule of its administration has not been established. Although comparative studies of adult patients undergoing HSCT have demonstrated enhanced efficacy and safety of twice-daily infusion (TD) compared with continuous infusion (CIF) of CsA, to our knowledge, similar studies have not yet been performed in pediatric groups. PROCEDURE: A self-administered questionnaire was used to retrospectively compare the clinical outcome and incidence of CsA-associated adverse events of 70 pediatric acute myelogenous leukemia patients who were receiving CsA by TD (n = 36) or CIF (n = 34) as GVHD prophylaxis for their first allogeneic HSCT. RESULTS: The cumulative incidences of grade II-IV acute GVHD and chronic GVHD, as well as the overall survival and event-free survival rates, did not differ significantly between the TD and CIF groups; however, the incidence of severe hypertension was significantly higher in the CIF group than the TD group. CONCLUSIONS: The analysis presented here indicates that TD and CIF administration of CsA have similar prophylactic effect on pediatric GVHD and suggest that TD is associated with a lower rate of toxicity than CIF in pediatric patients undergoing HSCT. Pediatr Blood Cancer 2015;62:291-298. © 2014 Wiley Periodicals, Inc.

Clinical course of juvenile myelomonocytic leukemia in the blast crisis phase treated by acute myeloid leukemia-oriented chemotherapy and allogeneic hematopoietic stem cell transplantation.

Juvenile myelomonocytic leukemia (JMML) is a mixed myeloproliferative and myelodysplastic disorder that occurs in early childhood. The clinical course of JMML is highly variable. A third of patients follow a relatively indolent course, although approximately 15% cases are thought to develop acute myeloid leukemia, referred to as blast crisis. The etiology and clinical characteristics of blast crisis remain unclear. We document the case of a 27-month-old boy who presented with hepatosplenomegaly, skin rash, and lymphadenopathy. An initial diagnosis of acute erythroid leukemia was made according to the French-American-British classification. Following estimation of hypersensitivity to GM-CSF and genetic analysis of PTPN11, he was diagnosed with JMML in the blast crisis phase. Although he had several poor prognostic factors, including monosomy 7 and high HbF percentage, he achieved partial remission after treatment with acute myeloid leukemia-oriented chemotherapy followed by allogeneic hematopoietic stem cell transplantation. He has been in complete remission for over 6 years.

Non-invasive renal artery embolization for renal dysplasia accompanied by hypertension.

Renovascular hypertension caused by renal dysplasia often is resistant to drug therapy. For a 14-year-old girl with such refractory hypertension, a non-invasive right renal ablation by embolization with anhydrous ethanol using a shepherd 's-crook' balloon catheter, was done. Blood pressure then rapidly normalized. Apart from mild fever after the procedure, no adverse effects occurred. In patients with mild renal artery stenosis and hypertension resistant to anti-hypertensive drug therapy, renal artery embolization may be a useful option.

Cyclosporin A may cause injury to undifferentiated glomeruli persisting in patients with Alport syndrome.

BACKGROUND/AIMS: Alport syndrome (AS) is a renal disorder caused by a genetic abnormality of type IV collagen α3 and α4, or α5 genes and shows a poor prognosis. Since the defect of type IV collagen synthesis disturbs the maturation process of the glomerular capillary loop, residual immature glomeruli persist after birth. The therapeutic efficacy of cyclosporin A (CyA) for AS patients seems to be controversial. We recently noted that renal specimens obtained from a child with AS who was treated with CyA and then developed CyA nephropathy included an increased number of undifferentiated embryonic-type glomeruli. METHODS: We analyzed renal histologic and immunohistologic findings in children with AS who did (n = 3) or did not (n = 2) develop CyA-induced nephropathy despite appropriately low serum CyA concentrations (<100 ng/mL) being maintained over a period of 2 years. To discriminate embryonic-type from mature glomeruli, staining for type IV collagen α1, laminin ß1, and laminin ß2 accompanied by light microscopic observation were employed. Staining patterns were used to semiquantitatively assess glomerular immaturity (glomerular immaturity index, or GII). RESULTS: In initial biopsy specimens, residual embryonic-type glomeruli were observed in each patient. Patients with early-onset CyA nephropathy had a high GII (median value 2.91 vs 1.23 ± 0.62 normal kidney tissues). In the follow-up biopsy after CyA treatment, surviving embryonic-type, collapsing embryonic-type, and sclerotic glomeruli that had failed to differentiate were observed. Taken together, the number of these glomeruli essentially equaled the total number of embryonic-type glomeruli in specimens obtained before CyA treatment. CONCLUSIONS: Our findings indicate a need for caution in CyA therapy for patients with AS, even for a relatively short course of administration, because some patients may have an unexpected number of embryonic-type glomeruli that predispose to CyA nephropathy.

Appropriate modulation of autophagy sensitizes malignant peripheral nerve sheath tumor cells to treatment with imatinib mesylate.

Malignant peripheral nerve sheath tumor (MPNST), very rare in childhood, is a highly aggressive soft-tissue tumor. We experienced a case of a 7-year-old boy with MPNST who was treated with imatinib mesylate (imatinib) after the identification of platelet-derived growth factor receptor expression in his tumor. We were unable to observe clinical benefits of imatinib in this patient. Therefore, cellular reactions of imatinib were investigated in vitro using 3 MPNST cell lines. Imatinib induced cytotoxicity in vitro with variable IC50 values (11.7 to >30 µM). Induction of apoptosis was not a pivotal mechanism in the inhibitory effects. We found that the treatment of MPNST cell lines with imatinib induced autophagy. Suppression of the initiation of autophagy by 3-methyladenine or small interfering RNA (siRNA) against beclin-1 attenuated the imatinib-mediated cytotoxicity. In contrast, blocking the formation of autophagosomes or the development of autolysosomes using siRNA against microtubule-associated protein light chain 3B, bafilomycin A1, chloroquine, or an MEK1/2 inhibitor (U0126) enhanced the imatinib-induced cytotoxicity in MPNST cells. Our data showed that the imatinib-mediated autophagy can function as a cytotoxic mechanism and that appropriate modulation of autophagy may sensitize MPNST cells to imatinib, which in turn may be a novel therapeutic strategy for MPNST.

Guillain-Barré syndrome and Crohn disease: a case report.

Development of both Crohn disease and Guillain-Barré syndrome likely involves autoimmunity associated with excessive inflammatory cytokines. We treated a girl who developed Guillain-Barré syndrome during the course of Crohn disease. Although high-dose γ-globulin therapy administered initially for Guillain-Barré syndrome was ineffective, plasmapheresis ameliorated her acute neuropathic symptoms. Crohn disease was managed with Salazopyrin administration and enteral feeding. Chronic inflammation of the intestinal mucosa caused by Crohn disease can allow presentation of microbial intestinal antigens normally hidden from the immune system. Such presentation could incite an extraintestinal immune response on the basis of molecular mimicry, leading to activation of systemic autoimmunity against the nervous system. Accordingly, concurrence of Guillain-Barré syndrome and Crohn disease in our patient appeared to result from shared autoimmune mechanisms and systemic and local increases in cytokine concentrations. The patient also developed erythema nodosum and gall stones, relatively common complications of Crohn disease. However, Guillain-Barré syndrome is rare.