Immunoglobulin abnormalities in patients with myotonic dystrophy

Hypogammaglobulinemia and infection risk in myotonic dystrophy type 1

INTRODUCTION/AIMS

Hypogammaglobulinemia is a common yet under-recognized feature of myotonic dystrophy type 1 (DM1). The aims of our study were to determine the frequency of immunoglobulin G (IgG) deficiency in our cohort, to examine the association between immunoglobulin levels and cytosine-thymine-guanine (CTG) repeat length in the DMPK gene, and to assess whether IgG levels are associated with an increased risk of infection in DM1 patients.

METHODS

We conducted a single-center, retrospective cross-sectional study of 65 adult patients with DM1 who presented to the Neuromuscular Clinic at Concord Repatriation General Hospital, Sydney, Australia, between January 2002 and January 2022. We systematically collected and analyzed clinical, laboratory, and genetic data for all patients with available serum electrophoresis and/or IgG level results.

RESULTS

Forty-one percent of DM1 patients had IgG deficiency despite normal lymphocyte counts, IgA, IgM, and albumin levels. There was an association between CTG repeat expansion size and the degree of IgG deficiency (F = 6.3, p = .02). There was no association between IgG deficiency and frequency of infection in this group (p = .428).

DISCUSSION

IgG deficiency is a frequent occurrence in DM1 patients and is associated with CTG repeat expansion size. Whether hypogammaglobulinemia is associated with increased infection risk in DM1 is unclear. A prospective multicenter cohort study is needed to evaluate this.

Prophylactic immunoglobulin therapy for pediatric congenital myotonic dystrophy

Congenital Myotonic Dystrophy (CMD) is an autosomal dominant hereditary disease caused by mutations in the dystrophia myotonica protein kinase gene. Patients with CMD often exhibit low immunoglobulin (Ig) G levels. While Ig replacement therapy for low IgG levels has been reported in several adult cases, there have been no reports on pediatric patients. This study presents a first pediatric case where Ig replacement therapy effectively eliminated susceptibility to infections. The CMD patient, a 1-year-old Japanese female with a history of premature birth and necrotizing enterocolitis, developed recurrent severe bacterial infections due to hypogammaglobulinemia. Intravenous immunoglobulin (IVIG) (600 mg/kg/month) was administered but failed to maintain sufficient serum trough IgG levels. The dosage was increased to 2 g/kg/month, and later, the treatment shifted to subcutaneous immunoglobulin (SCIG), resulting in a stable serum trough IgG level above 700 mg/dL for one year. The cause of hypogammaglobulinemia in CMD patients remains unclear, but potential mechanisms, including IgG-mediated hypercatabolism by alterations in the neonatal Fc receptor, have been considered. Genetic testing ruled out common variable immunodeficiency, and other potential causes were excluded. The study suggests that higher doses of IVIG or SCIG can effectively prevent severe infections associated with CMD-induced hypogammaglobulinemia in children.

Microbiota dysbiosis influences immune system and muscle pathophysiology of dystrophin-deficient mice

Duchenne muscular dystrophy (DMD) is a progressive severe muscle-wasting disease caused by mutations in DMD, encoding dystrophin, that leads to loss of muscle function with cardiac/respiratory failure and premature death. Since dystrophic muscles are sensed by infiltrating inflammatory cells and gut microbial communities can cause immune dysregulation and metabolic syndrome, we sought to investigate whether intestinal bacteria support the muscle immune response in mdx dystrophic murine model. We highlighted a strong correlation between DMD disease features and the relative abundance of Prevotella. Furthermore, the absence of gut microbes through the generation of mdx germ-free animal model, as well as modulation of the microbial community structure by antibiotic treatment, influenced muscle immunity and fibrosis. Intestinal colonization of mdx mice with eubiotic microbiota was sufficient to reduce inflammation and improve muscle pathology and function. This work identifies a potential role for the gut microbiota in the pathogenesis of DMD.

Blood Transcriptome Profiling Links Immunity to Disease Severity in Myotonic Dystrophy Type 1 (DM1)

The blood transcriptome was examined in relation to disease severity in type I myotonic dystrophy (DM1) patients who participated in the Observational Prolonged Trial In DM1 to Improve QoL- Standards (OPTIMISTIC) study. This sought to (a) ascertain if transcriptome changes were associated with increasing disease severity, as measured by the muscle impairment rating scale (MIRS), and (b) establish if these changes in mRNA expression and associated biological pathways were also observed in the Dystrophia Myotonica Biomarker Discovery Initiative (DMBDI) microarray dataset in blood (with equivalent MIRS/DMPK repeat length). The changes in gene expression were compared using a number of complementary pathways, gene ontology and upstream regulator analyses, which suggested that symptom severity in DM1 was linked to transcriptomic alterations in innate and adaptive immunity associated with muscle-wasting. Future studies should explore the role of immunity in DM1 in more detail to assess its relevance to DM1.

Role of Immunoglobulins in Muscular Dystrophies and Inflammatory Myopathies

Muscular dystrophies and inflammatory myopathies are heterogeneous muscular disorders characterized by progressive muscle weakness and mass loss. Despite the high variability of etiology, inflammation and involvement of both innate and adaptive immune response are shared features. The best understood immune mechanisms involved in these pathologies include complement cascade activation, auto-antibodies directed against muscular proteins or de-novo expressed antigens in myofibers, MHC-I overexpression in myofibers, and lymphocytes-mediated cytotoxicity. Intravenous immunoglobulins (IVIGs) administration could represent a suitable immunomodulator with this respect. Here we focus on mechanisms of action of immunoglobulins in muscular dystrophies and inflammatory myopathies highlighting results of IVIGs from pre-clinical and case reports evidences.

Enhanced serum immunoglobulin G clearance in myotonic dystrophy-associated hypogammaglobulinemia: a case series and review of the literature

BACKGROUND

Myotonic dystrophy type 1 is an autosomal dominant disorder characterized by muscle weakness, myotonia, cataracts, and cardiac conduction defects; it is associated with expansions of cytosine-thymine-guanine repeats in the myotonic dystrophy protein kinase. Hypogammaglobulinemia is a lesser known association of myotonic dystrophy type 1 and the underlying pathogenesis of immunoglobulin G depletion remains unclear.

CASE PRESENTATION

Here we report a kindred of two members (a 62-year-old white woman and a 30-year-old white man; mother and son) with myotonic dystrophy type 1-associated hypogammaglobulinemia associated with altered intravenous immunoglobulin elimination kinetics and reduced half-life. There was no history of systemic immunosuppression or renal or gastrointestinal protein loss in either patient, and no underlying case for a secondary immunodeficiency could be found. One patient required fortnightly intravenous immunoglobulin to maintain adequate trough immunoglobulin G levels.

CONCLUSIONS

Ongoing study of myotonic dystrophy type 1-associated hypogammaglobulinemia using contemporary tools of genomic medicine may help to further delineate the pathogenesis of this entity.

Massive abscess with prolonged respiratory failure due to newly diagnosed myotonic dystrophy: A case report

RATIONALE

Myotonic dystrophy is a progressive multisystem genetic heterogeneous disorder. General anesthesia with opioids increases the risk of prolonged postanesthetic respiratory recovery in myotonic dystrophy patients.

PATIENT CONCERNS

A 20-year-old previously healthy woman was transferred to our emergency department for further workup of respiratory failure, and massive ascites with abscess caused by endometriosis. Hypercapnic respiratory failure persisted under intensive care unit (ICU) management, but finally improved after cessation of fentanyl as a sedative agent.

DIAGNOSIS

Myotonic dystrophy type 1.

INTERVENTIONS

Massive ascites with abscess was accordingly managed by drainage, antibiotics, and an antifungal agent. Myotonic dystrophy type 1 was confirmed after molecular genetic testing revealed a cytosine-thymine-guanine repeat length of 400 to 450 in the DMPK gene.

OUTCOMES

The patient was discharged without complications on hospital day 69.

LESSONS

Myotonic dystrophy should be considered when hypercapnic respiratory failure persists in sedated ICU patients. Opioids should not be used for perioperative management of patients with myotonic dystrophy.

A review of the immunologic findings observed in retinitis pigmentosa

Most patients suffering from retinitis pigmentosa (RP) inherit the disorder; however, the immune-pathologic features associated with this disease have yet to be extensively studied. Six reports correlate antiretinal immune activity with vision deterioration in RP patients. Some of these patients have sporadic RP that occurs in excess of expected gene segregation during inheritance. The hypothesis that a primary immune-mediated disease process occurs in this sporadic group is supported by significant associations of RP with autoimmune endocrinopathies and other immune-related conditions or factors; however, no immunologic difference regarding RP family history is reported in the peripheral blood studies of RP patients. Twenty-one percent to 51% of RP patients display antiretinal antibodies, whereas 19-58% have antiretinal lymphocyte reactivity to retinal extract, and 60-85% have activated T cells. Mutations in animal models of RP have been shown to cause endoplasmic reticulum stress that may initiate immunopathology for genetic RP, but oxidative stress also encourages immune cytotoxicity. In addition, necrotic cell death is evident, which promotes inflammatory conditions. We review mechanisms and evidence for an occult inflammation in genetic RP and examine reports of efficacy in retarding RP progression with anti-inflammatory agents in clinical trials.

IgG deficiency and expansion of CTG repeats in myotonic dystrophy

OBJECTIVES

Expansion of CTG repeats in myotonic dystrophy (DM1) alters the regulated expression of numerous genes. It is considered to explain the major clinical features of DM1. IgG deficiency is common in DM1 and is due to altered FcRn-related hypercatabolism. We hypothesized that the IgG catabolic rate is correlated with CTG repeat expansion.

METHODS

Correlations between serum immunoglobulin levels, peripheral lymphocyte subset counts and CTG repeat numbers were performed in 52 DM1 patients.

RESULTS

Serum IgG and IgG1 levels were below the normal limit respectively in 54% and 72% of patients. Increasing CTG repeat numbers were significantly correlated with decreasing serum IgG and IgG1 levels, and with decreasing CD3(+) T-cell and CD3(+)-CD8(+) cell counts. An abnormal immunoglobulin profile at protein electrophoresis was found in 4 patients.

CONCLUSION

We conclude that the catabolic rate of IgG is linked to expanded CTG repeats, possibly involving an altered immune response.

Genetic syndromic immunodeficiencies with antibody defects

This article reviews the major syndromic immunodeficiencies with significant antibody defects, many of which may require intravenous immunogammaglobulin therapy. The authors define syndromic immunodeficiency as an illness associated with a characteristic group of phenotypic abnormalities or laboratory features that comprise a recognizable syndrome. Many are familial with a defined inheritance pattern. Immunodeficiency may not be a major part of the illness and may not be present in all patients; thus, these conditions differ from primary immunodeficiency syndromes, in which immune abnormalities are a consistent and prominent feature of their disease.

Syndromic immunodeficiencies: genetic syndromes associated with immune abnormalities

In syndromic immunodeficiencies, clinical features not directly associated with the immune defect are prominent. Patients may present with either infectious complications or extra-immune medical issues. In addition to the immunologic abnormality, a wide range of organ systems may be affected. Patients may present with disturbances in skeletal, neurologic, dermatologic, or gastrointestinal function or development. These conditions can be caused by developmental abnormalities, chromosomal aberrations, metabolic disorders, or teratogens. For a number of these conditions, recent advances have resulted in an enhanced understanding of their genetic basis. The finding of immune deficits in a number of defined syndromes with congenital anomalies suggests that an underlying genetic syndrome should be considered in those patients in whom a significant non-immune feature is present.

Reduction of serum IgG level and peripheral T-cell counts are correlated with CTG repeat lengths in myotonic dystrophy patients

Myotonic dystrophy (DM) is an autosomal dominant multisystem disorder associated with expansion of the CTG repeat within the 3' non-coding region of the myotonin protein kinase (MT-PK) gene. CTG repeat length has been shown to correlate with the clinical category and age at onset of the disease. The relationship between CTG repeat length and immunological parameters were analyzed in this study. We determined CTG repeat length in 14 DM patients and 15 normal controls using Southern and PCR analyses, and then correlated their CTG repeat lengths with their serum immunoglobulin (IgG, IgA, IgM) levels and the number of peripheral white blood cells, including lymphocyte subsets. In DM patients, increasing CTG repeat lengths correlated significantly with decreasing serum IgG levels, decreasing total lymphocyte counts, and decreasing CD2+, CD3+, and CD4+ cell counts. Immunological parameters were also influenced by the expansion of CTG repeat in DM patients.

Sialic acid content in serum IgG from patients with myotonic dystrophy compared with healthy controls

One of the determinants of the lifetime of circulating glycoproteins is their content of the terminal carbohydrate sialic acid. In order to elucidate a possible mechanism behind reduced concentration of IgG in patients with myotonic dystrophy, serum IgG was isolated by affinity chromatography and its content of sialic acid determined. No difference between patients and healthy controls was found. The results provide further support to the idea that a host factor rather than an abnormality of the IgG molecule itself is responsible for the low concentration of serum IgG in this disease.