Complex medical history of a patient with a compound heterozygous mutation in C1QC

Two siblings with monogenic lupus due to C1qC deficiency and case based review

Monogenic lupus is an extremely rare clinical condition in children. Defects in the complement pathway are the most common causes of monogenic lupus. C1qC deficiency is one of the defects in this pathway and is even rarer. Herein, we present two cases of monogenic lupus diagnosed with C1qC deficiency in siblings. In addition, a literature search was conducted for articles on monogenic lupus due to C1qC deficiency. We found 14 articles. Our literature search identified 17 paediatric patients with monogenic lupus associated with C1qC deficiency. 10 (58%) of the reported patients were female. The median age at diagnosis of patients in the literature was 3 years. Mucocutaneous involvement was remarkable in all cases of C1qC deficiency. Joint involvement was reported in about half of the cases. Approximately half of the reported cases has suffered from recurrent infections. 38% of the cases have had CNS involvement and 25% of these had nephritis. While both of our patients had mucocutaneous involvement, one of our patients had recurrent EBV infection. ANA was positive, anti-dsDNA was negative, C3-C4 levels were normal in almost all cases in the reported cases. The anti-Sm and anti-SSA positivities of these cases were also remarkable. These laboratory findings were similar in our patients. The G34R mutation of the C1qC gene is the most common genetic defect identified to date. We found a GRCh38/Hg38 1p36.12 homozygous deletion in the C1qC gene in both of our patients. It is necessary to investigate the causes of monogenic lupus in patients with early-onset lupus, history of consanguineous marriages, and antibody positivity.

Update on hereditary C1q deficiency: pathophysiology, clinical presentation, genotype and management

PURPOSE OF REVIEW

C1q deficiency is a rare inborn error of immunity characterized by susceptibility to severe infections and profound immune dysregulation, with a systemic lupus erythematosus-like phenotype. The management of patients with C1q deficiency is challenged by the rarity of this condition and the wide clinical variability. This review aims to emphasize the importance of a thorough immunological and clinical characterization to help guide a personalized and comprehensive approach to patients.

RECENT FINDINGS

We focus on the concept of C1q deficiency as a bridge between the monogenic form of systemic lupus erythematosus and the Mendelian type I interferonopathies. Moreover, we explore the role of new treatment strategies such as Janus-associated kinase (JAK) inhibitors and allogeneic stem cell transplantation.

SUMMARY

In this narrative review, we provide a systematic overview of C1q deficiency, starting with the description of the pathophysiological background and the variable clinical phenotype, and then exploring the different prognoses, the consequent treatment strategies and future directions.

Proteomics in Patients with Fibromyalgia Syndrome: A Systematic Review of Observational Studies

PURPOSE OF REVIEW

Fibromyalgia syndrome (FMS) is a disease of unknown pathophysiology, with the diagnosis being based on a set of clinical criteria. Proteomic analysis can provide significant biological information for the pathophysiology of the disease but may also reveal biomarkers for diagnosis or therapeutic targets. The present systematic review aims to synthesize the evidence regarding the proteome of adult patients with FMS using data from observational studies.

RECENT FINDINGS

An extensive literature search was conducted in MEDLINE/PubMed, CENTRAL, and clinicaltrials.gov from inception until November 2022. The study protocol was published in OSF. Two independent reviewers evaluated the studies and extracted data. The quality of studies was assessed using the modified Newcastle-Ottawa scale adjusted for proteomic research. Ten studies fulfilled the protocol criteria, identifying 3328 proteins, 145 of which were differentially expressed among patients with FMS against controls. The proteins were identified in plasma, serum, cerebrospinal fluid, and saliva samples. The control groups included healthy individuals and patients with pain (inflammatory and non-inflammatory). The most important proteins identified involved transferrin, α-, β-, and γ-fibrinogen chains, profilin-1, transaldolase, PGAM1, apolipoprotein-C3, complement C4A and C1QC, immunoglobin parts, and acute phase reactants. Weak correlations were observed between proteins and pain sensation, or quality of life scales, apart from the association of transferrin and a2-macroglobulin with moderate-to-severe pain sensation. The quality of included studies was moderate-to-good. FMS appears to be related to protein dysregulation in the complement and coagulation cascades and the metabolism of iron. Several proteins may be dysregulated due to the excessive oxidative stress response.

Neuroinflammation Associated With Inborn Errors of Immunity

The advent of high-throughput sequencing has facilitated genotype-phenotype correlations in congenital diseases. This has provided molecular diagnosis and benefited patient management but has also revealed substantial phenotypic heterogeneity. Although distinct neuroinflammatory diseases are scarce among the several thousands of established congenital diseases, elements of neuroinflammation are increasingly recognized in a substantial proportion of inborn errors of immunity, where it may even dominate the clinical picture at initial presentation. Although each disease entity is rare, they collectively can constitute a significant proportion of neuropediatric patients in tertiary care and may occasionally also explain adult neurology patients. We focus this review on the signs and symptoms of neuroinflammation that have been reported in association with established pathogenic variants in immune genes and suggest the following subdivision based on proposed underlying mechanisms: autoinflammatory disorders, tolerance defects, and immunodeficiency disorders. The large group of autoinflammatory disorders is further subdivided into IL-1β-mediated disorders, NF-κB dysregulation, type I interferonopathies, and hemophagocytic syndromes. We delineate emerging pathogenic themes underlying neuroinflammation in monogenic diseases and describe the breadth of the clinical spectrum to support decisions to screen for a genetic diagnosis and encourage further research on a neglected phenomenon.

Circulating C1q levels in health and disease, more than just a biomarker

C1q is the recognition molecule of the classical pathway of the complement system. By binding to its targets, such as antigen-bound immunoglobulins or C-reactive protein, C1q contributes to the innate defense against infections. However, C1q also plays several other roles beyond its traditional role in complement activation. Circulating levels of C1q are determined in routine diagnostics as biomarker in several diseases. Decreased C1q levels are present in several autoimmune conditions. The decreased levels reflect the consumption of C1q by complement activation and serves as a biomarker for disease activity. In contrast, increased C1q levels are present in infectious and inflammatory diseases and may serve as a diagnostic biomarker. The increased levels of C1q are still incompletely understood but are suggested to modulate the adaptive immune response as C1q is known to impact on the maturation status of antigen-presenting cells and C1q impacts directly on T cells leading to decreased T-cell activity in high C1q conditions. In this review, we provide a comprehensive overview of the current literature on circulating levels of C1q in health and disease, and discuss how C1q can both protect against infections as well as maintain tolerance by regulating adaptive immunity.