No abstract

Objective. To describe the clinical features, genotype, and treatment in a series of subjects with confirmed adenosine deaminase 2 (ADA2) deficiency.Methods. All symptomatic subjects were referred for genetic testing for suspected ADA2 deficiency; relatives of index cases were also screened. Demographic, clinical, and laboratory characteristics and treatments were recorded. Genetic analyses included whole-exome sequencing in 4 subjects and Sanger sequencing of CECR1 (the gene for cat eye syndrome chromosome region candidate 1) in all subjects. Assays for ADA2 enzyme activity and quantitative polymerase chain reaction analysis of CECR1 messenger RNA (mRNA) were also performed.Results. We identified 15 subjects with ADA2 deficiency, 5 of whom were asymptomatic (relatives of index cases; ages 5-42 years). Homozygous or compound heterozygous mutations in CECR1 were identified in all subjects. Phenotypic manifestations in the patients with symptomatic ADA2 deficiency included livedo racemosa (73.3%), neurologic involvement (53.3%), and immunodeficiency (46.7%). CECR1 mRNA expression in 8 subjects, including 5 who were presymptomatic, was significantly lower than in healthy controls (P 5 0.0016). Subjects with ADA2 deficiency (with or without symptoms) also had lower ADA2 enzyme activity compared to healthy pediatric controls (P < 0.0001) and patients with sporadic (nonfamilial) childhood polyarteritis nodosa (PAN) without CECR1 mutation (P 5 0.0108). Anti2tumor necrosis factor therapy was required in 9 of the 10 symptomatic subjects.Conclusion. The clinical manifestations of ADA2 deficiency ranged in severity from limited cutaneous involvement to severe multisystemic vasculitis; one-third of our cases (5 of 15) were currently asymptomatic, and required close monitoring. We recommend CECR1 screening for unaffected siblings of index cases, cases of familial vasculitis, and cases of PAN that is resistant to standard treatment.

Standing et al. report a novel autoinflammatory disease caused by a homozygous missense mutation in the actin-regulating protein WDR1. The disease is characterized by periodic fevers, immunodeficiency, and thrombocytopenia, with increased polymerized actin in immune cells and increased IL-18 secretion.

Cryopyrin-associated periodic syndrome (CAPS) is caused by gain-of-function NLRP3 mutations. Recently, somatic NLRP3 mosaicism has been reported in some CAPS patients who were previously classified as “mutation-negative.” We describe here the clinical and laboratory findings in eight British adult patients who presented with symptoms typical of CAPS other than an onset in mid-late adulthood. All patients underwent comprehensive clinical and laboratory investigations, including analysis of the NLRP3 gene using Sanger and amplicon-based deep sequencing (ADS) along with measurements of extracellular apoptosis-associated speck-like protein with CARD domain (ASC) aggregates. The clinical phenotype in all subjects was consistent with mid-spectrum CAPS, except a median age at disease onset of 50 years. Sanger sequencing of NLRP3 was non-diagnostic but ADS detected a somatic NLRP3 mutation in each case. In one patient, DNA isolated from blood demonstrated an increase in the mutant allele from 5 to 45% over 12 years. ASC aggregates in patients’ serum measured during active disease were significantly higher than healthy controls. This series represents 8% of CAPS patients diagnosed in a single center, suggesting that acquired NLRP3 mutations may not be an uncommon cause of the syndrome and should be sought in all patients with late-onset symptoms otherwise compatible with CAPS. Steadily worsening CAPS symptoms in one patient were associated with clonal expansion of the mutant allele predominantly affecting myeloid cells. Two patients developed AA amyloidosis, which previously has only been reported in CAPS in association with life-long germline NLRP3 mutations.