Complement C1s deficiency in a male Caucasian patient with systemic lupus erythematosus: a case report

Deficiencies of the early complement components of the classical pathway (CP) are well-documented in association with systemic lupus erythematosus (SLE) or SLE-like syndromes and severe pyogenic infections. Among these, complete C1s deficiency has been reported in nine cases so far. Here, we describe a 34-year-old male patient who presented with severe, recurrent infections since childhood, including meningitides with pneumococci and meningococci, erysipelas, subcutaneous abscess, and recurrent infections of the upper airways. The patient also exhibited adult-onset SLE, meeting 7/11 of the ACR criteria and 34 of the 2019 EULAR/ACR classification criteria, along with class IV-G (A) proliferative lupus nephritis (LN). A screening of the complement cascade showed immeasurably low CH50, while the alternative pathway (AP) function was normal. Subsequent determination of complement components revealed undetectable C1s with low levels of C1r and C1q, normal C3, and slightly elevated C4 and C2 concentrations. The patient had no anti-C1q antibodies. Renal biopsy showed class IV-G (A) LN with complement C1q positivity along the glomerular basement membranes (GBMs) and weak deposition of IgG, IgM, and complement C3 and C4 in the mesangium and GBM. In an ELISA-based functional assay determining C4d deposition, the patient's absent complement activity was fully restored by adding C1s. The genome of the patient was analyzed by whole genome sequencing showing two truncating variants in the C1S gene. One mutation was located at nucleotide 514 in exon 5, caused by a nucleotide substitution from G to T, resulting in a nonsense mutation from Gly172 (p.Gly172*). The other mutation was located at nucleotide 750 in exon 7, where C was replaced by a G, resulting in a nonsense mutation from Tyr250 (p.Tyr250*). Both mutations create a premature stop codon and have not previously been reported in the literature. These genetic findings, combined with the absence of C1s in the circulation, strongly suggest a compound heterozygote C1s deficiency in our patient, without additional defect within the complement cascade. As in a previous C1s deficiency case, the patient responded well to rituximab. The present case highlights unanswered questions regarding the CP's role in SLE etiopathogenesis.

Hereditary angioedema: a case report and literature review

Hereditary angioedema is an autosomal dominant condition with a typical presentation of diffuse edematous, painless, and nonpitting swelling of the soft tissues. The disease manifests itself primarily in the extremities, face, airway, and abdominal viscera. Proper diagnosis and treatment are essential as this condition has the capacity of becoming life-threatening due to potential airway embarrassment. This case report demonstrates the complexity of diagnosing and treating hereditary angioedema. Hereditary angioedema often is overlooked on a differential diagnosis of patients suffering from diffuse swelling and/or abdominal discomfort. Nonetheless, the diagnosis of hereditary angioedema should be included when assessing patients who display the proper symptomology and familial history of the condition.

Angioedema in the emergency department: a presentation of lymphoma

A 58-year-old woman presented to emergency departments on several occasions with episodic angioedema. Lymphoplasmacytic lymphoma with an IgM paraprotein (Waldenstrom's macroglobulinemia) was eventually diagnosed 14 months later in association with acquired C1 esterase inhibitor deficiency. Resolution of the angioedema and C1 esterase inhibitor deficiency was achieved with danazol and treatment of the underlying lymphoma.

Molecular basis of a selective C1s deficiency associated with early onset multiple autoimmune diseases

We have investigated the molecular basis of selective and complete C1s deficiency in 2-year-old girl with complex autoimmune diseases including lupus-like syndrome, Hashimoto's thyroiditis, and autoimmune hepatitis. This patient's complement profile was characterized by the absence of CH50 activity, C1 functional activity <10%, and undetectable levels of C1s Ag associated with normal levels of C1r and C1q Ags. Exon-specific amplification of genomic DNA by PCR followed by direct sequence analysis revealed a homozygous nonsense mutation in the C1s gene exon XII at codon 534, caused by a nucleotide substitution from C (CGA for arginine) to T (TGA for stop codon). Both parents were heterozygous for this mutation. We used the new restriction site for endonuclease Fok-1 created by the mutation to detect this mutation in the genomic DNA of seven healthy family members. Four additional heterozygotes for the mutation were identified in two generations. Our data characterize for the first time the genetic defect of a selective and complete C1s deficiency in a Caucasian patient.

Molecular basis of human complement C1s deficiency

This is the first report on the molecular basis of human complement C1s deficiency. Two abnormalities in the C1s gene were identified in a Japanese family, including one patient, by using exon-specific PCR, single-strand conformation polymorphism analysis, and nucleotide sequencing. A deletion of 4 bp, TTTG, was identified in exon X when using genomic DNA from the patient, his father, and his paternal grandmother. They were all heterozygous for the mutation. The mutant gene encodes a truncated C1s from the N terminus to the short consensus repeat domain. By further sequencing the PCR products, a nonsense mutation from G to T was identified at codon 608 in exon XII in the patient, his mother, and his sister. They were all heterozygous for the nonsense mutation. The mutant gene encodes a truncated form of C1s that lacks the C-terminal 80 amino acids. These results indicate that the patient was a compound heterozygote with the 4-bp deletion on the paternal allele and the nonsense mutation on the maternal allele. The levels of serum C1s seem to be correlated to the genotypes of the C1s gene in which no C1s was detected in the patient, and one-half of the normal level in the family members who are heterozygous for either mutation. The present study demonstrates that the disease is inherited in an autosomal recessive mode.

Selective complement C1s deficiency caused by homozygous four-base deletion in the C1s gene

The complement system plays an important role in defense mechanisms by promoting the adherence of microorganisms to phagocytic cells and lysis of foreign organisms. Deficiencies of the first complement components, C1r/C1s, often cause systemic lupus erythematosus-like syndromes and severe pyogenic infections. Up to now no genetic analysis of the C1r/C1s deficiencies has been carried out. In the present work, we report the first genetic analysis of selective C1s deficiency, the patient having a normal amount of C1r. C1s RNA with a normal size was detected in patient's subcutaneous fibroblasts (YKF) by RNA blot analysis and RT-PCR. The amount of C1s RNA was approximately one-tenth of the RNA from the human chondrosarcoma cell line, HCS2/8. In contrast, the levels of C1r and beta-actin RNA of YKF were similar to that of HCS2/8. Sequence analysis of C1s cDNA revealed a deletion at nucleotides 1087-1090 (TTTG), creating a stop codon (TGA) at position 94 downstream of the mutation site. Direct sequencing of the gene between the primers designed on intron 9 and exon 10 indicated the presence of the deletion on exon 10 of the gene. Quantitative Southern blot hybridization suggested the mutation was homozygous. The 4-bp deletion on exon 10 was also found in the patient's heterozygous mother who had normal hemolytic activity.

Non-coordinated biosynthesis of early complement components in a deficiency of complement proteins C1r and C1s

We report on a 60-year-old woman with systemic lupus erythematosus and a total (95%) C1r and a partial (36%) C1s deficiency. The patient complained about cutaneous lesions on forearms and legs without other systemic involvement. Elevated anti-nuclear, anti-native DNA and anti-SSA antibodies were present. The finding of persistently depressed levels of haemolytic complement activity (CH50) on both serum and plasma, associated with normal levels of C3, C4 and C2 components, and normal alternative pathway haemolytic activity showed a deficiency of an early component of the classical pathway. Indeed C1r component was below the limits of detection whereas C1s component was lowered (36%). The depressed CH50 was only corrected by purified C1r. Biosynthesis of C1r and C1s by patient's monocytes was spontaneously normal but not up-regulated by interferon-gamma for C1r alone, whereas the biosynthesis of C1s, but also of interleukin-6, was increased, indicating a specific disregulation of C1r. The deficiency was associated with a lupus syndrome and a fatal assumed septic shock. This is in agreement with other reported cases.

The Fine Page: angiotensin converting enzyme angioedema

Angioedema/urticaria secondary to ACE inhibitor drugs is an important clinical entity, which dermatologists should be aware of as they are so widely used and their use will undoubtedly increase. In addition to the obvious importance to the patient of promptly recognizing ACE inhibitor angioedema, uncovering the etiology of angioedema/urticaria is a rare and satisfying experience that can "make your day."

Selective deficiency of C1s associated with a systemic lupus erythematosus-like syndrome. Report of a case

We describe a patient who developed a systemic lupus erythematosus-like syndrome characterized by bilateral malar erythema, antinuclear antibody, and anti-double-stranded DNA antibody. He was started on hemodialysis (3 times/week) because of renal failure. He completely lacked total hemolytic complement (CH50) activity, which was subsequently determined to be due to the absence of the first component of complement (C1). The specificity was further defined, by Ouchterlony analysis using anti-C1s antiserum, and was found to be the C1 subcomponent C1s. There was no absence of C1r. We conclude that this is a case of selective deficiency of C1s.

Hereditary angioedema: its diagnostic and management perspectives

Although hereditary angioedema accounts for only a small fraction of all cases of angioedema, it is the most common genetically linked clinical disorder caused by the deficiency of a protein associated with complement activation. Attacks may be complicated by incapacitating cutaneous swelling, life-threatening upper airway impediment, and severe gastrointestinal colic. Recent physicochemical and genetic studies have contributed significantly to our understanding of the structure of the inhibitor protein. Measurement of serum C4 titer is an efficacious screening test. Normal levels during symptomatic periods rule out the diagnosis, whereas decreased levels warrant determination of C1 esterase inhibitor titer by immunoassay or functional assay. The functional assay is necessary to ascertain the genetic variant form. The importance of making the correct diagnosis cannot be overemphasized. It can avert potentially fatal consequences, such as upper airway obstruction and unnecessary abdominal surgery. The application of short-term preventive measures can avoid complications associated with trauma. Finally, abatement or elimination of symptoms in patients with incessant and disabling attacks can be attained by long-term therapy with currently available attenuated androgens.

[Clinical features, pathogenesis, and therapy of hereditary angioneurotic edema (author's transl)]

The hereditary angioneurotic edema is probably a more frequent disease than presumed until now. It is inherited as an autosomal dominant trait, and is due to diminished or functionally deficient C1 esterase inhibitor. Family history is negative in cases of spontaneous mutations. Two thirds of the patients are already affected in infancy with peripheral edema, facial edema, abdominal symptoms and/or edema of the glottis occuring spontaneously or secondary to trauma. Recently the prognosis has become better due to early diagnosis and the possibility of substitution therapy with C1 esterase inhibitor. A long-term prophylaxis may be achieved with synthetic androgens.

[Hereditary angioedema by defict of C1 esterase. Our experience in 8 cases]

Eight cases of hereditary angioedema, all of them with low values of C1-sterase inhibitor are analyzed. In 7 cases the C3 and C4 components of the complement were assessed; the results showed marked descent of C4. The 8 patients came from 4 different families; only 2 of them were males. Six patients presented digestive disorders, reporting colic pain, nausea and vomiting. In 1 of them the abdominal picture was the only evidence of the disease. In 5 patients the angioedema episodes occurred following traumatisms and in 3 because of emotional states. The duration of the attacks varied from several hours to six days. There was a familial history in all cases. Three of the patients had repeated episodes of pharyngolaryngeal angioedema, two of them requiring emergency tracheotomy because of suffocating crisis. Six patients were treated with Epsilon aminocaproic acid (16 to 20 gr daily) or with tranexamic acid (1 to 3 gr. daily). In 4 cases the results were excellent with either of these antifibrinolytic drugs. No side effects were observed in the tranexamic acid therapy whilst they were frequent in the treatment with Epsilon aminocaproic acid.