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Imaging of patient 1. (A) Muscle MRI of both legs performed at the age of 5 years: coronal gadolinium-enhanced T1-weighted sequence at different levels, showing patchy inflammatory muscular lesions. (B) Cerebral MRI performed at the age of 7 years. Left: axial gadolinium-enhanced T1-weighted sequence, showing gadolinium-enhanced mesencephalic (up) and peduncular (down) lesions. Right: axial diffusion-weighted sequence showing mesencephalic (up) and peduncular (down) hyperintensities. (C) Cerebral MRI performed 4 months later: axial gadolinium-enhanced T1-weighted sequence showing evolution towards lacunar lesions (up: mesencephalic lesions/down: peduncular lesions). (D) Cerebral MRI performed 3 years later: gadolinium-enhanced T1-weighted sequences showing lacunar lesions located in the internal capsule.
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MRI and positron emission tomography (PET) scan revealed inflammatory lesions of the limbs (figure 1A). Muscle biopsy identified focal necrotising angiitis compatible with periarteritis nodosa. MRI showed gadolinium-enhancing lesions with subtle abnormality diffusion sequences suggestive of a vascular stroke (figure 1B), which was later confirmed by their evolution into lacunar lesions a few months later (figure 1C). The recent MRI showed the occurrence of another asymptomatic lacunar lesion of the internal capsule (figure 1C). The expression of a panel of other cytokine transcripts was not significantly altered (see online supplementary figure S1).
Illustration of the mutation and ADA2 activity. (A) Sanger sequencing analysis illustrating the point c.1358A>G mutation which was identified in both sisters. (B) Reverse quantitative PCR (RQ-PCR, copy number calculated) illustrating the exon 7 deletion in the two sisters and in the father. CECR1-E7a and CECR1-E7b are two distinct amplicons encompassing exon 7 of CECR1 gene, to avoid a possible rare polymorphism in a primer hybridisation site. (C) CECR1 mutations result in a decrease in ADA2 activity in patient plasma. The figure shows the ADA2 activity in the plasma of the two patients tested on two occasions, compared with ADA2 activity in the plasma of four controls (***p<0.001).
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CECR1 sequencing revealed a heterozygous c.1358A>G; p.Tyr453Cys mutation in both siblings (figure 2A). PCR revealed a heterozygous deletion of exon 7 (c.973-?_1081+?del; p.Val325Thrfs*7), predicted to lead to a frameshift and truncated protein in both children (figure 2B). Parental analysis (father's genotype: c.[973-?_1081+?del];[=]; mother's genotype: c.[1358A>G];[=]) confirmed that the sisters were compound heterozygous for these two lesions.
IFN and neutrophil gene expression studies. The RQ value for each transcript is equal to the normalised fold change relative to a control. (A) Quantitative reverse transcription PCR of a panel of six IFN-1-stimulated genes in CECR1 mutation-positive sisters on two occasions. IFN score was 4.82 before treatment and 1.86 after treatment in patient 1 and 11.79 and 9.47 before treatment in patient 2. IFN-stimulated genes are variably overexpressed in the two patients. (B) The expression of a panel of neutrophil-stimulated genes was measured in patients 1 and 2 on two occasions. Neutrophil-stimulated gene expression was essentially similar to that in controls. IFN-1, interferon 1; NA, not applicable; RQ value, relative quantification value.
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The expression of a panel of IFN-stimulated genes was significantly elevated in both patients (figure 3A), though for the older sister the second sampling showed no elevation of IFN-stimulated genes. Neutrophil-stimulated genes were not overexpressed (figure 3B).