Aicardi-Goutieres syndrome (AGS) is a genetic encephalopathy whose clinical features mimic those of acquired in utero viral infection. AGS exhibits locus heterogeneity, with mutations identified in genes encoding the 3'-->5' exonuclease TREX1 and the three subunits of the RNASEH2 endonuclease complex. To define the molecular spectrum of AGS, we performed mutation screening in patients, from 127 pedigrees, with a clinical diagnosis of the disease. Biallelic mutations in TREX1, RNASEH2A, RNASEH2B, and RNASEH2C were observed in 31, 3, 47, and 18 families, respectively. In five families, we identified an RNASEH2A or RNASEH2B mutation on one allele only. In one child, the disease occurred because of a de novo heterozygous TREX1 mutation. In 22 families, no mutations were found. Null mutations were common in TREX1, although a specific missense mutation was observed frequently in patients from northern Europe. Almost all mutations in RNASEH2A, RNASEH2B, and RNASEH2C were missense. We identified an RNASEH2C founder mutation in 13 Pakistani families. We also collected clinical data from 123 mutation-positive patients. Two clinical presentations could be delineated: an early-onset neonatal form, highly reminiscent of congenital infection seen particularly with TREX1 mutations, and a later-onset presentation, sometimes occurring after several months of normal development and occasionally associated with remarkably preserved neurological function, most frequently due to RNASEH2B mutations. Mortality was correlated with genotype; 34.3% of patients with TREX1, RNASEH2A, and RNASEH2C mutations versus 8.0% RNASEH2B mutation-positive patients were known to have died (P=.001). Our analysis defines the phenotypic spectrum of AGS and suggests a coherent mutation-screening strategy in this heterogeneous disorder. Additionally, our data indicate that at least one further AGS-causing gene remains to be identified.

Eight infants developed a progressive disorder of the central nervous system with bilateral spasticity and dystonia, acquired microcephaly, and a rapid course toward profound deterioration and death. All the patients had abnormal cerebrospinal fluid with mild but persistent lymphocytosis. Computed tomography showed various combinations of bilateral symmetrical calcifications in the basal ganglia, progressive brain atrophy, and deep white matter hypodensities, the first two being present in all families but not in every individual patient. The disorder is familial and probably genetic in origin, although some features, especially the pleocytosis, may erroneously suggest an inflammatory condition.

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Twenty-seven patients with familial encephalopathy with calcification of the basal ganglia and chronic cerebrospinal fluid (CSF) lymphocytosis (Aicardi-Goutières syndrome) are reviewed. In 19 children, the onset was within the first 4 months of life. Most patients had normal head circumference at birth, but 21 developed microcephaly between 3 and 12 months. Neuroimaging showed severe and progressive brain atrophy in all patients. The extent and intensity of the calcification was variable even in the same sibship. CSF lymphocytosis persisted beyond 12 months of age in 7 children. High levels of interferon-alpha were found in serum and CSF in 14 patients. The higher CSF levels suggest intrathecal synthesis. Tubuloreticular inclusions related to the presence of interferon were found in 4 additional children. The 19 patients still alive (6 older than 10 years) are profoundly disabled. However, the syndrome may present with individual variations in severity, rapidity of evolution, and imaging features. Neuropathological examination in 2 patients failed to detect significant inflammatory lesions and showed only foci of necrosis and wide-spread demyelination. This study supports an autosomal recessive inheritance for this syndrome. The high level of interferon-alpha is not explained but may play a role in the pathogenesis of the disorder.

A new cerebral disorder, described in three unrelated children, has recognizable clinical, radiologic, and neuropathologic findings. The onset occurs from early infancy to adolescence with slowing of cognitive performance, rare convulsive seizures, and a mixture of extrapyramidal, cerebellar, and pyramidal signs. CT shows progressive calcifications in the basal and cerebellar gray nuclei and the central white matter. MRI reveals diffuse abnormal signals of the white matter on T2-weighted sequences. A special feature is the development of parenchymal cysts in the cerebellum and the supratentorial compartment, leading to compressive complications and surgical considerations. Neuropathologic examination of surgically removed pericystic samples reveals angiomatous-like rearrangements of the microvessels, together with degenerative secondary changes of other cellular elements. Both the anatomic findings and the course of the disease suggest a constitutional, diffuse cerebral microangiopathy resulting in microcystic, then macrocystic, parenchymal degeneration.

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Paroxysmal extreme pain disorder is a highly distinctive sodium channelopathy with incompletely carbamazepine-sensitive bouts of pain and sympathetic nervous system dysfunction. It is most likely to be misdiagnosed as epilepsy and, particularly in infancy, as hyperekplexia and reflex anoxic seizures.

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