Fatoş Yalçınkaya

Mutant Adenosine Deaminase 2 in a Polyarteritis Nodosa Vasculopathy

BACKGROUND Polyarteritis nodosa is a systemic necrotizing vasculitis with a pathogenesis that is poorly understood. We identified six families with multiple cases of systemic and cutaneous polyarteritis nodosa, consistent with autosomal recessive inheritance. In most cases, onset of the disease occurred during childhood. METHODS We carried out exome sequencing in persons from multiply affected families of Georgian Jewish or German ancestry. We performed targeted sequencing in additional family members and in unrelated affected persons, 3 of Georgian Jewish ancestry and 14 of Turkish ancestry. Mutations were assessed by testing their effect on enzymatic activity in serum specimens from patients, analysis of protein structure, expression in mammalian cells, and biophysical analysis of purified protein. RESULTS In all the families, vasculitis was caused by recessive mutations in CECR1, the gene encoding adenosine deaminase 2 (ADA2). All the Georgian Jewish patients were homozygous for a mutation encoding a Gly47Arg substitution, the German patients were compound heterozygous for Arg169Gln and Pro251Leu mutations, and one Turkish patient was compound heterozygous for Gly47Val and Trp264Ser mutations. In the endogamous Georgian Jewish population, the Gly47Arg carrier frequency was 0.102, which is consistent with the high prevalence of disease. The other mutations either were found in only one family member or patient or were extremely rare. ADA2 activity was significantly reduced in serum specimens from patients. Expression in human embryonic kidney 293T cells revealed low amounts of mutant secreted protein. CONCLUSIONS Recessive loss-of-function mutations of ADA2, a growth factor that is the major extracellular adenosine deaminase, can cause polyarteritis nodosa vasculopathy with highly varied clinical expression. (Funded by the Shaare Zedek Medical Center and others.).

MEFV mutations in Turkish patients suffering from familial Mediterranean fever

Familial Mediterranean fever (FMF) is a recessive inherited disorder affecting Sephardic Jews, Arabs, Armenians and Turks. The gene responsible for FMF was recently cloned and several disease‐associated mutations have been described. We have evaluated seven MEFV mutations in 460 chromosomes of 230 unrelated patients with FMF living in Turkey, using PCR methods. The M694V allele accounted for 43.5% of the alleles studied and 19.1% of the patients were homozygous. The M680I, V726A and M694I mutations were responsible for 12.0%, 11.1% and 2.8% of the patients respectively. R761H, K695R and E148Q were rarely encountered. Two thirds of the disease alleles were attributed to three common mutations: M694V, M680V and V726A, but only 54% of the patients carried one or two of the three mutations. Adding the four rarer mutations increased these figures to 72% and 60%, respectively. Altogether, 79.6% of the patients bore at least one of the main mutations, and 84.3% carried at least one of the seven mutations studied. The 28 patients suffering also from amyloidosis carried at least one of five mutations, M694V being the most common. These results suggest that the origin of FMF in Turkey is heterogenous, all common mutations are associated with amyloidosis. Further, rapid and accurate molecular diagnosis of FMF is feasible in most cases. Hum Mutat 15:118–119, 2000.

Digestion of Chromatin in Apoptotic Cell Microparticles Prevents Autoimmunity

Antibodies to DNA and chromatin drive autoimmunity in systemic lupus erythematosus (SLE). Null mutations and hypomorphic variants of the secreted deoxyribonuclease DNASE1L3 are linked to familial and sporadic SLE, respectively. We report that DNASE1L3-deficient mice rapidly develop autoantibodies to DNA and chromatin, followed by an SLE-like disease. Circulating DNASE1L3 is produced by dendritic cells and macrophages, and its levels inversely correlate with anti-DNA antibody response. DNASE1L3 is uniquely capable of digesting chromatin in microparticles released from apoptotic cells. Accordingly, DNASE1L3-deficient mice and human patients have elevated DNA levels in plasma, particularly in circulating microparticles. Murine and human autoantibody clones and serum antibodies from human SLE patients bind to DNASE1L3-sensitive chromatin on the surface of microparticles. Thus, extracellular microparticle-associated chromatin is a potential self-antigen normally digested by circulating DNASE1L3. The loss of this tolerance mechanism can contribute to SLE, and its restoration may represent a therapeutic opportunity in the disease.

MEFV Mutations Modify the Clinical Presentation of Henoch-Schonlein Purpura

Objective To investigate the prevalence of MEFV gene mutations in Turkish patients with Henoch-Schönlein purpura (HSP) but with no symptoms of familial Mediterranean fever (FMF). In addition, we assessed the clinical and laboratory characteristics of HSP patients with and without MEFV mutations. Methods Eighty pediatric patients with HSP (44 boys and 36 girls) were enrolled. Blood for mutation analysis was obtained either at the time of the diagnosis of HSP or during followup visits in previously diagnosed patients. No patient had the diagnosis of FMF in their history and in the followup period. Exon 10 of the MEFV gene was screened, together with p.E148Q mutation analysis. Results Twenty-seven (34%) patients were found to be heterozygous for one of the screened MEFV mutations; p.M694V in 16, p.M680I in 5, p.V726A in 3, and p.E148Q in 3 patients. Patients with MEFV mutations were younger than those without mutations and they had edema and arthritis more frequently. Also, the frequencies of elevated erythrocyte sedimentation rate and C-reactive protein values were found to be significantly higher in patients who had MEFV mutations. Conclusion Alterations in the MEFV gene are important susceptibility factors for the development of HSP and also affect the clinical presentation of it.

Familial Mediterranean Fever — Amyloidosis and the Val726Ala Mutation

To the Editor: Familial Mediterranean fever is an autosomal recessive disorder characterized by acute attacks of fever and inflammation of serous tissues. The disease affects certain ethnic groups,...

Anti-IL-1 treatment in familial Mediterranean fever and related amyloidosis.

Colchicine is the standard treatment in familial Mediterranean fever (FMF) patients. New treatment strategies are needed in FMF patients who were unresponsive to colchicine therapy or who had developed amyloidosis. The aim of this study was to present clinical-laboratory features and treatment responses of pediatric FMF patients that were treated with anti-IL-1 therapies. Files of patients who had been followed in our department with diagnosis of FMF were retrospectively evaluated. Patients that have been receiving anti-IL-1 therapies (anakinra or canakinumab) were included to the study. All patients were interpreted with respect to the demographic data, clinical and laboratory features of the disease, genetic analysis of MEFV mutations and treatment responses. Among 330 currently registered FMF patients, 13 patients were included to the study. Seven of them received anti-IL-1 therapy due to colchicine resistance and 6 due to FMF-related amyloidosis (1 of them with nephrotic syndrome, 2 with chronic kidney disease, 3 with renal transplantation). In all treated patients, attacks completely disappeared or decreased in frequency; partial remission occured in nephrotic syndrome patient; and their life quality improved. Anti-IL-1 therapies can be successfully used in colchicine-resistant FMF patients and patients with amyloidosis during childhood and adolescent period without major side effects.

Nutcracker syndrome in children: the role of upright position examination and superior mesenteric artery angle measurement in the diagnosis.

The purpose of this study was to evaluate the pathophysiologic characteristics of nutcracker syndrome (NS) and to assess the role of upright position imaging and superior mesenteric artery (SMA) angle measurement in the diagnosis.

DNASE1L3 Mutations in Hypocomplementemic Urticarial Vasculitis Syndrome

OBJECTIVE Hypocomplementemic urticarial vasculitis syndrome (HUVS) is characterized by recurrent urticaria along with dermal vasculitis, arthritis, and glomerulonephritis. Systemic lupus erythematosus (SLE) develops in >50% of patients with HUVS, although the pathogenesis is unknown. The aim of this study was to identify the causative DNA mutations in 2 families with autosomal-recessive HUVS, in order to reveal the pathogenesis and facilitate the laboratory diagnosis. METHODS Autozygosity mapping was combined with whole-exome sequencing. RESULTS In a family with 3 affected children, we identified a homozygous frameshift mutation, c.289_290delAC, in DNASE1L3. We subsequently identified another homozygous DNASE1L3 mutation leading to exon skipping, c.320+4delAGTA, in an unrelated family. The detected mutations led to loss of function, via either nonsense-mediated messenger RNA decay or abolished endonuclease activity, as demonstrated by a plasmid nicking assay. CONCLUSION These results show that HUVS is caused by mutations in DNASE1L3, encoding an endonuclease that previously has been associated with SLE.

LRIG2 Mutations Cause Urofacial Syndrome

Urofacial syndrome (UFS) (or Ochoa syndrome) is an autosomal-recessive disease characterized by congenital urinary bladder dysfunction, associated with a significant risk of kidney failure, and an abnormal facial expression upon smiling, laughing, and crying. We report that a subset of UFS-affected individuals have biallelic mutations in LRIG2, encoding leucine-rich repeats and immunoglobulin-like domains 2, a protein implicated in neural cell signaling and tumorigenesis. Importantly, we have demonstrated that rare variants in LRIG2 might be relevant to nonsyndromic bladder disease. We have previously shown that UFS is also caused by mutations in HPSE2, encoding heparanase-2. LRIG2 and heparanase-2 were immunodetected in nerve fascicles growing between muscle bundles within the human fetal bladder, directly implicating both molecules in neural development in the lower urinary tract.

Hypertension induced reversible posterior leukoencephalopathy syndrome: a report of two cases.

Reversible posterior leukoencephalopathy syndrome (RPLS) is a recently described disorder with typical radiological findings of bilateral grey and white matter abnormalities in the posterior regions of the cerebral hemispheres. The majority of patients with RPLS are adults and it is rare in children. In this report, two patients with RPLS are presented. In the first patient the primary diagnosis was acute post-streptococcal glomerulonephritis, a known cause of RPLS both in adults and in children. The second patient had Henoch Schönlein purpura. Conclusion:These patients are presented to highlight the importance of reversible posterior leukoencephalopathy syndrome. As the spectrum of associated diseases is diverse, paediatricians must be aware of this syndrome in order to initiate appropriate management.