Antibody deficiency and isolated growth hormone deficiency in a girl with Mulibrey nanism

Mulibrey nanism and immunological complications: a comprehensive case report and literature review

Introduction

Mulibrey nanism (MUL) is a rare disorder caused by TRIM37 gene variants characterized by growth failure, dysmorphic features, congestive heart failure (CHF), and an increased risk of Wilms' tumor. Although immune system impairment has been documented in MUL, the underlying mechanisms remain poorly understood.

Methods

We present a case of MUL with progressive lymphopenia and review similar cases from the literature.

Results

Our patient presented with prenatal onset growth restriction, characteristic dysmorphic features, and Wilms' tumor. She developed progressive lymphopenia starting at 10 years of age, leading to the initiation of intravenous immunoglobulin (IVIG) replacement therapy and infection prophylaxis. Genetic analysis detected a likely pathogenic variant on the maternal allele and copy number loss on the paternal allele in TRIM37. Subsequently a cardiac magnetic resonance imaging was conducted revealing signs of pericardial constriction raising concerns for intestinal lymphatic losses. The cessation of IVIG therapy did not coincide with any increase in the rate of infections. The patient exhibited a distinct immunological profile, characterized by hypogammaglobulinemia, impaired antibody responses, and skewed T-cell subsets with an altered CD4+/CD8+ ratio, consistent with previous reports. Normal thymocyte development assessed by artificial thymic organoid platform ruled out an early hematopoietic intrinsic defect of T-cell development.

Discussion

The immunological profile of MUL patients reported so far shares similarities with that described in protein-losing enteropathy secondary to CHF in Fontan circulation and primary intestinal lymphangiectasia. These similarities include hypogammaglobulinemia, significant T-cell deficiency with decreased CD4+ and CD8+ counts, altered CD4+/CD8+ ratios, and significantly modified CD4+ and CD8+ T-cell phenotypes toward effector and terminal differentiated T cells, accompanied by a loss of naïve CD45RA+ T lymphocytes. In MUL, CHF is a cardinal feature, occurring in a significant proportion of patients and influencing prognosis. Signs of CHF or constrictive pericarditis have been evident in the case reported here and in all cases of MUL with documented immune dysfunction reported so far. These observations raise intriguing connections between these conditions. However, further investigation is warranted to in-depth define the immunological defect, providing valuable insights into the pathophysiology and treatment strategies for this condition.

The TRIM37 variants in Mulibrey nanism patients paralyze follicular helper T cell differentiation

The Mulibrey (Muscle-liver-brain-eye) nanism caused by loss-of-function variants in TRIM37 gene is an autosomal recessive disorder characterized by severe growth failure and constrictive pericarditis. These patients also suffer from severe respiratory infections, co-incident with an increased mortality rate. Here, we revealed that TRIM37 variants were associated with recurrent infection. Trim37 FIN_major (a representative variant of Mulibrey nanism patients) and Trim37 knockout mice were susceptible to influenza virus infection. These mice showed defects in follicular helper T (T_FH) cell development and antibody production. The effects of Trim37 on T_FH cell differentiation relied on its E3 ligase activity catalyzing the K27/29-linked polyubiquitination of Bcl6 and its MATH domain-mediated interactions with Bcl6, thereby protecting Bcl6 from proteasome-mediated degradation. Collectively, these findings highlight the importance of the Trim37-Bcl6 axis in controlling the development of T_FH cells and the production of high-affinity antibodies, and further unveil the immunologic mechanism underlying recurrent respiratory infection in Mulibrey nanism.

CD4+ T Cell Defects in a Mulibrey Patient With Specific TRIM37 Mutations

Mulibrey (muscle-liver-brain-eye) syndrome (MUL) is an autosomal recessive disorder caused by mutations in the TRIpartite motif (TRIM)37 gene, encoding for TRIM37 a member of the TRIM E3 ubiquitin ligase protein family. MUL patients are characterized by growth retardation, dysmorphic features, and a wide range of abnormalities affecting different organs. However, T-cell abnormalities have not been observed in MUL subjects, to date. Here we described the immunological features of a MUL child carrying recently identified TRIM37 mutations, a 17q22 deletion of maternal origin combined with a TRIM37 variant of paternal origin. Here we found quantitative and functional defects in CD4⁺ T cells from this MUL case. Low levels of TRIM37 protein were specifically detected in CD4⁺ T cells of MUL patient and associated with their altered proliferation and cytokine production. Of note, both CD4⁺ and CD8⁺ T lymphocytes of MUL child displayed an effector memory phenotype compared with healthy children. This clinical case research highlighted the possible role of TRIM37 in the control of immune cell number and function, especially in CD4⁺ T cells. Finally, this study may contribute to the novel mechanistic studies aim of identifying, in depth, the role of the TRIM37 protein in the immune system.

TRIMming down to TRIM37: Relevance to Inflammation, Cardiovascular Disorders, and Cancer in MULIBREY Nanism

TRIpartite motif (TRIM) proteins are part of the largest subfamilies of E3 ligases that mediate the transfer of ubiquitin to substrate target proteins. In this review, we focus on TRIM37 in the normal cell and in pathological conditions, with an emphasis on the MULIBREY (MUscle-LIver-BRain-EYe) genetic disorder caused by TRIM37 mutations. TRIM37 is characterized by the presence of a RING domain, B-box motifs, and a coiled-coil region, and its C-terminal part includes the MATH domain specific to TRIM37. MULIBREY nanism is a rare autosomal recessive caused by TRIM37 mutations and characterized by severe pre- and postnatal growth failure. Constrictive pericarditis is the most serious anomaly of the disease and is present in about 20% of patients. The patients have a deregulation of glucose and lipid metabolism, including type 2 diabetes, fatty liver, and hypertension. Puzzlingly, MULIBREY patients, deficient for TRIM37, are plagued with numerous tumors. Among non-MULIBREY patients affected by cancer, a wide variety of cancers are associated with an overexpression of TRIM37. This suggests that normal cells need an optimal equilibrium in TRIM37 expression. Finding a way to keep that balance could lead to potential innovative drugs for MULIBREY nanism, including heart condition and carcinogenesis treatment.

A novel mutation in TRIM37 is associated with mulibrey nanism in a Turkish boy

Mulibrey nanism is a rare autosomal-recessive disorder characterized by prenatal onset severe growth retardation and pericardial constriction associated with abnormalities of muscle, liver, brain and eye. More than 80% of previously reported patients are of Finnish origin in whom a founder mutation in the TRIM37 gene have been described. We report on a 7-year-old Turkish boy who presented with classical phenotypic features of mulibrey nanism. Mutation screening of the TRIM37 gene revealed that the proband had a homozygous two base pair deletion, c.1894_1895delGA, resulting in a frame-shift and a premature termination codon. Our proband is one of the rare examples of mulibrey nanism outside Finland and extends the mutation spectrum in this disorder.

Wilms' tumor and novel TRIM37 mutations in an Australian patient with mulibrey nanism

Mulibrey nanism is a rare autosomal recessive growth disorder with prenatal onset, including occasional progressive cardiopathy, characteristic facial features, failure of sexual maturation, insulin resistance with type 2 diabetes, and an increased risk for Wilms' tumor. Mulibrey nanism is prevalent in the Finnish population and appears extremely rare elsewhere. However, cases outside of Finland may be underdiagnosed or misdiagnosed as having the 3-M or Silver-Russell syndrome, two important differential diagnostic disorders. Here, we report the first Australian patient with mulibrey nanism, in whom the occurrence of Wilms' tumor suggested the correct diagnosis. This was confirmed by the identification of two novel mutations in tripartite motif protein 37 (TRIM37) encoding a RING finger ubiquitin E3 ligase. Both mutations, the p.Cys109Ser B-box missense mutation and the p.Glu271_Ser287del in-frame deletion in the tumor necrosis factor receptor associated factor (TRAF) domain alter the subcellular localization of TRIM37. As both the B-box and the TRAF domains are predicted to be important for mediating the protein-protein interactions, these mutations may help the understanding of the cellular interactions of TRIM37. Our findings imply the importance of early molecular diagnostics in cases of suspected mulibrey nanism and of identifying novel mutations with potential relevance for unraveling the underlying molecular pathology. Ultrasound surveillance for Wilms' tumor is recommended for children with mulibrey nanism.

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.

Mulibrey nanism: clinical features and diagnostic criteria

Mulibrey nanism (MUL) is an autosomal recessive disease caused by mutations in the TRIM37 gene encoding the peroxisomal TRIM37 protein of unknown function. In this work, we analysed the clinical characteristics of 85 Finnish patients with MUL, most of whom were homozygous for the Finn major mutation of TRIM37. The patients' hospital records from birth to the time of the diagnosis at age 0.02-52 years (median 2.1 years) were retrospectively analysed. All except four of the patients (95%) had a prenatal onset growth failure without postnatal catch up growth. The mean length standard deviation score (SDS) was -3.1 and -4.0 at birth and at diagnosis, respectively. In infancy, feeding difficulties, and respiratory tract infections were the most common problems. Congestive heart failure and pericardial constriction were diagnosed during infancy in 12% and 6% of the patients, respectively. At the time of the diagnosis, characteristic craniofacial features of scaphocephaly, facial triangularity, high and broad forehead, and low nasal bridge were evident in over 90% of the patients. In addition, practically all patients were gracile and had thin extremities. Other findings included a peculiar high-pitched voice (96%), yellowish dots in ocular fundi (79%), cutaneous naevi flammei (65%), hepatomegaly (45%), and fibrous dysplasia of long bones (25%). Mild muscular hypotonicity (68%) was the only neurological abnormality. The clinical features of the Finnish patients with MUL formed a distinct entity. The most consistent findings were growth failure and characteristic craniofacial features. However, organ manifestations varied considerably in early childhood. Based on these findings, we propose new diagnostic criteria for MUL.

Physical linkage of the human growth hormone gene cluster and the CD79b (Ig beta/B29) gene

We have previously characterized a locus control region for the GH1 gene consisting of four DNase I hypersensitive sites (HS) located between 14.5 and 32 kb 5' to the GH1 gene transcription start site. Sequence analysis of the region between the GH1 gene and its most proximal HS (HSI) revealed a perfect match to the B-lymphocyte-specific CD79b gene. Restriction mapping and hybridization analysis of YAC and cosmid clones confirmed the close linkage of the CD79b gene to the hGH gene cluster and facilitated the assembly of a 100-kb physical map linking the hGH locus, the CD79b gene, and the more distant muscle-specific sodium channel alpha-subunit (SCN4A) gene.

Immunodeficiency as a component of recognizable syndromes

Immunodeficiency occurs in numerous genetic syndromes. While it is the dominant manifestation in primary immunodeficiencies, immune deficits may also be seen in a variety of other recognizable syndromes. Immunodeficiency has been reported in 64 such conditions, adding to the 45 recognized primary immunodeficiencies. These uncommon syndromes with immune defects can present with: (a) growth deficiency (11 syndromes with disproportionate or proportionate short stature), (b) specific organ system dysfunction (18 with gastrointestinal, dermatologic, or neurologic abnormalities), (c) inborn errors of metabolism (13), (d) miscellaneous anomalies (10), or (e) chromosome anomalies (12). In most of the disorders, only some of the affected patients have immune defects. However, in 27 syndromes, immunodeficiency is a constant finding. We briefly review the clinical manifestations of each syndrome and delineate the specific associated immune defects. In most syndromes, the connection between the immune and other defects is unknown. Recognition of these conditions involving both the immune and other organ systems may facilitate accurate diagnosis and management as well as yield information regarding genes critical for the development of the involved systems.

X-linked agammaglobulinemia. A clinical and molecular analysis

X-linked agammaglobulinemia (XLA), characterized by a profound deficiency of B lymphocytes due to an arrest in B lymphocyte development, is caused by mutations in the gene encoding Btk (Bruton tyrosine kinase). The BTK gene has been cloned and the genomic organization determined. BTK codes for 19 exons and is expressed in all hematopoietic cell lineages but is selectively down-regulated in T lymphocytes and plasma cells. The different Btk domains include PH, TH, SH3, SH2, and the kinase (SH1) domains. Btk, a cytoplasmic protein tyrosine kinase, is involved in cell signaling, although the precise pathway remains elusive. Mutation analysis has been performed in 236 families representing 282 patients. Mutations are scattered throughout the gene and consist of missense, nonsense, and splice site mutations as well as deletions and insertions. The major consequence of nonfunctional Btk appears to be a delay or block of the development of pro-B cells to pre-B cells and then to mature lymphocytes. Because IgG is actively transported across the placenta, affected newborns have normal levels of serum IgG at birth followed by gradually decreasing IgG levels and development of hypogammaglobulinemia and increased susceptibility to infections. Bacterial infections are the most common clinical manifestation. Resistance to viral infection is intact, except for an unusual susceptibility to infections with enteroviruses that may result in vaccine-related paralytic poliomyelitis or a dermatomyositis-meningoencephalitis syndrome. The diagnosis of XLA is based on the presence of lymphoid hypoplasia, markedly reduced serum levels of all 3 major classes of immunoglobulins, failure to make antibody to antigenic stimulation, and almost complete absence of B lymphocytes in the peripheral blood. Carrier detection and prenatal diagnosis are possible. The prophylactic infusion of high-dose intravenous immunoglobulin (IVIG) and the use of antibiotics have markedly improved the long-term prognosis of patients with XLA.