The Extended Clinical Phenotype of 26 Patients with Chronic Mucocutaneous Candidiasis due to Gain-of-Function Mutations in STAT1.

PURPOSE: Gain-of-function (GOF) mutations in the signal transducer and activator of transcription 1 (STAT1) result in unbalanced STAT signaling and cause immune dysregulation and immunodeficiency. The latter is often characterized by the susceptibility to recurrent Candida infections, resulting in the clinical picture of chronic mucocutaneous candidiasis (CMC). This study aims to assess the frequency of GOF STAT1 mutations in a large international cohort of CMC patients. METHODS: STAT1 was sequenced in genomic DNA from 57 CMC patients and 35 healthy family members. The functional relevance of nine different STAT1 variants was shown by flow cytometric analysis of STAT1 phosphorylation in patients' peripheral blood cells (PBMC) after stimulation with interferon (IFN)-α, IFN-γ or interleukin-27 respectively. Extended clinical data sets were collected and summarized for 26 patients. RESULTS: Heterozygous mutations within STAT1 were identified in 35 of 57 CMC patients (61%). Out of 39 familial cases from 11 families, 26 patients (67%) from 9 families and out of 18 sporadic cases, 9 patients (50%) were shown to have heterozygous mutations within STAT1. Thirteen distinct STAT1 mutations are reported in this paper. Eight of these mutations are known to cause CMC (p.M202V, p.A267V, p.R274W, p.R274Q, p.T385M, p.K388E, p.N397D, and p.F404Y). However, five STAT1 variants (p.F172L, p.Y287D, p.P293S, p.T385K and p.S466R) have not been reported before in CMC patients. CONCLUSION: STAT1 mutations are frequently observed in patients suffering from CMC. Thus, sequence analysis of STAT1 in CMC patients is advised. Measurement of IFN- or IL-induced STAT1 phosphorylation in PBMC provides a fast and reliable diagnostic tool and should be carried out in addition to genetic testing.

Rilonacept for colchicine-resistant or -intolerant familial Mediterranean fever: a randomized trial.

BACKGROUND: Currently, there is no proven alternative therapy for patients with familial Mediterranean fever (FMF) that is resistant to or intolerant of colchicine. Interleukin-1 is a key proinflammatory cytokine in FMF. OBJECTIVE: To assess the efficacy and safety of rilonacept, an interleukin-1 decoy receptor, in treating patients with colchicine-resistant or -intolerant FMF. DESIGN: Randomized, double-blind, single-participant alternating treatment study. (ClinicalTrials.gov number: NCT00582907). SETTING: 6 U.S. sites. PATIENTS: Patients with FMF aged 4 years or older with 1 or more attacks per month. INTERVENTION: One of 4 treatment sequences that each included two 3-month courses of rilonacept, 2.2 mg/kg (maximum, 160 mg) by weekly subcutaneous injection, and two 3-month courses of placebo. MEASUREMENTS: Differences in the frequency of FMF attacks and adverse events between rilonacept and placebo. RESULTS: 8 males and 6 females with a mean age of 24.4 years (SD, 11.8) were randomly assigned. Among 12 participants who completed 2 or more treatment courses, the rilonacept-placebo attack risk ratio was 0.59 (SD, 0.12) (equal-tail 95% credible interval, 0.39 to 0.85). The median number of attacks per month was 0.77 (0.18 and 1.20 attacks in the first and third quartiles, respectively) with rilonacept versus 2.00 (0.90 and 2.40, respectively) with placebo (median difference, -1.74 [95% CI, -3.4 to -0.1]; P = 0.027). There were more treatment courses of rilonacept without attacks (29% vs. 0%; P = 0.004) and with a decrease in attacks of greater than 50% compared with the baseline rate during screening (75% vs. 35%; P = 0.006) than with placebo. However, the duration of attacks did not differ between placebo and rilonacept (median difference, 1.2 days [-0.5 and 2.4 days in the first and third quartiles, respectively]; P = 0.32). Injection site reactions were more frequent with rilonacept (median difference, 0 events per patient treatment month [medians of -4 and 0 in the first and third quartiles, respectively]; P = 0.047), but no differences were seen in other adverse events. LIMITATION: Small sample size, heterogeneity of FMF mutations, age, and participant indication (colchicine resistance or intolerance) were study limitations. CONCLUSION: Rilonacept reduces the frequency of FMF attacks and seems to be a treatment option for patients with colchicine-resistant or -intolerant FMF. PRIMARY FUNDING SOURCE: U.S. Food and Drug Administration, Office of Orphan Products Development.

Mutations at opposite ends of the DIII/S4-S5 linker of sodium channel Na V 1.7 produce distinct pain disorders.

BACKGROUND: Two groups of gain-of-function mutations in sodium channel NaV1.7, which are expressed in dorsal root ganglion (DRG) neurons, produce two clinically-distinct pain syndromes - inherited erythromelalgia (IEM) and paroxysmal extreme pain disorder (PEPD). IEM is characterized by intermittent burning pain and skin redness in the feet or hands, triggered by warmth or mild exercise, while PEPD is characterized by episodes of rectal, ocular and mandibular pain accompanied with skin flushing, triggered by bowel movement and perianal stimulation. Most of the IEM mutations are located within channel domains I and II, while most of the PEPD mutations are located within domains III and IV. The structural dichotomy parallels the biophysical effects of the two types of mutations, with IEM mutations shifting voltage-dependence of NaV1.7 activation in a hyperpolarized direction, and PEPD mutations shifting fast-inactivation of NaV1.7 in a depolarized direction. While four IEM and four PEPD mutations are located within cytoplasmic linkers joining segments 4 and 5 (S4-S5 linkers) in the different domains (IEM: domains I and II; PEPD: domains III and IV), no S4-S5 linker has been reported to house both IEM and PEPD mutations thus far. RESULTS: We have identified a new IEM mutation P1308L within the C-terminus of the DIII/S4-S5 linker of NaV1.7, ten amino acids from a known PEPD mutation V1298F which is located within the N-terminus of this linker. We used voltage-clamp to compare the biophysical properties of the two mutant channels and current-clamp to study their effects on DRG neuron excitability. We confirm that P1308L and V1298F behave as prototypical IEM and PEPD mutations, respectively. We also show that DRG neurons expressing either P1308L or V1298F become hyperexcitable, compared to DRG neurons expressing wild-type channels. CONCLUSIONS: Our results provide evidence for differential roles of the DIII/S4-S5 linker N- and C-termini in channel inactivation and activation, and demonstrate the cellular basis for pain in patients carrying these mutations.