Evolution of genome diagnostics in epidermolysis bullosa: Unveiling the power of next-generation sequencing.

BACKGROUND: Genome diagnostics is considered gold standard diagnostics for epidermolysis bullosa (EB), a phenotypically and genetically heterogeneous group of rare disorders characterized by blistering and wounding of mucocutaneous tissues. EB is caused by pathogenic variants in genes encoding proteins of the dermo-epidermal junction. Accurate genetic diagnosis of EB is crucial for prognostication, counselling and precision-medicine. Genome diagnostics for EB started in 1991 with the introduction of Sanger sequencing (SS), analysing one gene at a time. In 2013, SS was superseded by next-generation sequencing (NGS), that allow for high-throughput sequencing of multiple genes in parallel. Several studies have shown a beneficial role for NGS in EB diagnostics, but its true benefit has not been quantified. OBJECTIVES: To determine the benefit of NGS in EB by systematically evaluating the performance of different genome diagnostics used over time based on robust data from the Dutch EB Registry. METHODS: The diagnostic performances of SS and NGS were systematically evaluated in a retrospective observational study including all index cases with a clinical diagnosis of EB in whom genome diagnostics was performed between 01 January 1994 and 01 January 2022 (n = 308), registered at the Dutch EB Expertise Centre. RESULTS: Over time, a genetic diagnosis was made in 289/308 (94%) EB cases. The diagnostic yield increased from 89% (SS) to 95% (NGS). Most importantly, NGS significantly reduced diagnostic turnaround time (39 days vs. 211 days, p < 0.001). The likelihood of detecting variants of uncertain significance and additional findings increased from 5% and 1% (SS) to 22% and 13% (NGS) respectively. CONCLUSIONS: Our study quantifies the benefit of NGS-based methods and demonstrate they have had a major impact on EB diagnostics through an increased diagnostic yield and a dramatically decreased turnaround time (39 days). Although our diagnostic yield is high (95%), further improvement of genome diagnostics is urgently needed to provide a genetic diagnosis in all EB patients.

Two cases of the caudal duplication anomaly including a discordant monozygotic twin.

We present two unrelated patients with various duplications in the caudal region. One patient presented with a duplication of the distal spine from L4, left double ureter, duplication of the vagina and cervix, and duplication of the distal colon. The second patient was diagnosed with a duplication of the colon, bladder, vagina and uterus. The first patient had an unaffected monozygotic twin sister. Dominguez et al. [1993: Am J Dis Child 147:1048-1052] presented six similar cases, and introduced the name "caudal duplication syndrome." The pathogenesis of the caudal duplication anomaly is unclear. The possibility of a polytopic primary developmental field defect or a disruptive sequence are discussed. On the other hand, somatic or germline mutations in certain developmental genes could be involved, as illustrated by the mouse mutations disorganisation and fused. DNA-analysis of the AXIN1 gene, the human homologue of the gene responsible for fused, performed in our first patient, did not show any apparent pathogenic mutation.

A role for MLH3 in hereditary nonpolyposis colorectal cancer.

We investigated a possible role of the mismatch-repair gene MLH3 in hereditary nonpolyposis colorectal cancer by scanning for mutations in 39 HNPCC families and in 288 patients suspected of having HNPCC. We identified ten different germline MLH3 variants, one frameshift and nine missense mutations, in 12 patients suspected of HNPCC. Three of the 12 also carried a mutation in MSH6.

Contralateral epileptiform transients in stroke (CETS).

Epileptiform discharges occurring either periodically (PLEDs) or nonperiodically ipsilateral to a cerebral infarction are well known. Also, bilateral independent periodic transients (BIPLEDs) can occur in strokes complicated by hypoxia and/or infection. We bring attention to an EEG event, not previously described to our knowledge, for which we propose the term "contralateral epileptiform transients in stroke (CETS)." This phenomenon is apparently rare and consists of nonperiodic spikes occurring singly and in bursts, sharp waves, or sharp-and-slow waves occurring contralaterally to an acute stroke. These discharges are unassociated with clinical seizure and appear to last longer than PLEDs or BIPLEDs. Sometimes, they may point to a contralateral cerebral and/or cardiac pathology.

Visual evoked response in head trauma: pattern-shift stimulus.

Studies of visual evoked potentials in head injuries have all utilized the flash stimulus. We studied the efficacy of monocular pattern-shift visual evoked potentials (PSVEPs) in eliciting residual dysfunction of the visual pathways in 33 patients 6 to 24 months after head injury. Those with ocular trauma or ocular pathology were not included. Abnormal PSVEPs were seen in one-third of 33 head-injured patients. Only 1 (11%) of 9 patients with mild cognitive impairment had abnormal PSVEPs compared with 7 (39%) of 18 with moderate and 3 (50%) of 6 with severe cognitive impairment.

Monocular pattern-shift visual evoked potentials in hemispheric strokes.

Monocular pattern-shift visual evoked potentials were obtained in (i) 33 patients with unilateral non-hemorrhagic hemispheric infarction (age 50-79 years; 23 males, 10 females), (ii) 21 age- and sex-matched patient controls (control group or CGI) with no remote or recent stroke, normal neurological examination and similar incidence of diabetes mellitus, hypertension and heart disease, and (iii) 21 age- and sex-matched healthy elderly community volunteers (CGII). Subjects with history of glaucoma, cataracts, other media opacities or symptomatic retinal lesions were not considered or included in any of the 3 study groups. In addition, all subjects in each of the 3 groups had a normal ocular and fundoscopic examination. The mean interocular P100 latency difference in the stroke group was significantly greater than that in CGI or II (P less than 0.01). The mean interocular P100 amplitude ratio (small P100/large P100) in the stroke subjects was significantly different from that of CGI or II (P less than 0.02). The mean P100 latency on ocular stimulation ipsilateral to the side of infarction was significantly longer than that of either left or right ocular stimulation in CGI or II (P less than 0.01). The mean P100 latency on ocular stimulation contralateral to the side of infarction was similarly but less significantly longer than that on left or right ocular stimulation in CGI or II (P less than 0.05). Evidence of anterior visual pathway dysfunction was thus elicited in the stroke population using the technique.

Gender factor in longer P100 latency of elderly persons.

Monocular pattern-shift visual evoked potentials (PSVEPs) were obtained in 26 neurologically and ophthalmologically normal elderly community volunteers (mean age 59.4, males 15, females 11), and compared with similarly obtained data in 26 sex-matched young subjects (mean age 28.1). Elderly males were age-matched with elderly females, and young males were age-matched with young females. Data analyses at both the midoccipital-linked ears and midoccipital-midcentral derivations revealed that the combined-eye mean P100 latency in the elderly as a whole was significantly longer than the young sex-matched controls (P less than 0.02). However, the latency in the elderly males was not significantly different from that of sex-matched young males, or age-matched elderly females. The latency in young female subjects, on the other hand, was significantly shorter both when compared to that of age-matched young males (P less than 0.01) and sex-matched elderly females (P less than 0.01). The differences in other PSVEP variables, namely, interocular P100 latency differences, P100 amplitudes and interocular P100 amplitude ratios were not significant between the groups and subgroups studied. It is concluded that females account for the major contribution towards the longer P100 latency in the elderly.

Electroencephalographic findings in urea-cycle disorders.

Eleven electroencephalograms in 4 infants with urea-cycle disorders were reviewed. All infants had one or more abnormal EEGs. The abnormalities consisted mainly of multiareal spikes, spike-waves, or sharp-and-slow-wave activity. In addition, one patient, a term infant, exhibited exaggerated spindle-delta bursts. This infant, and also one other at a similar age, had monorhythmic paroxysmal theta activity. Clinically, all patients had seizures shortly preceding abnormal EEGs. EEG alterations were encountered over a wide range of elevated serum ammonia levels. Normal EEGs occurred in the face of slightly elevated levels. It is concluded that epileptiform EEG alterations may be a characteristic manifestation of urea-cycle disorders.

An empirical link between lateral eye movements and lateralized event-related brain potentials.

Much recent research has been devoted to the investigation of lateral eye movements (LEMs) as an indicator of hemispheric activation. Various personality characteristics have been reported to be associated with predominant left and right looking which have been interpreted on the basis of hemispheric specialization; however, this interpretation has been challenged by others. We investigated the relationship between LEMs obtained in a paradigmatic question-asking procedure and event-related potentials (ERPs) in response to a checkerboard stimulus. Subjects were 20 right-handed young adults (11 men, 9 women). We found that left-looking subjects had a greater positive-going occipital ERP amplitude at 90-msec poststimulus on the right side than on the left; the reverse was true for right-looking subjects (F = 11.08, 1/16 df, p < 0.005).

Fourteen and six c/sec positive bursts in comatose patients.

Of ten patients with Reye's syndrome, there were five with stage II or III coma where EEGs revealed 14 c/sec positive bursts in a background of diffuse delta waves. Positive bursts disappeared upon EEG improvement in two survivors and when the EEG became nearly isoelectric in two other patients. Although 14 and 6 c/sec positive bursts are seen commonly during sleep in normal young persons, their occurence in association with diffuse delta waves in acutely ill, comatose patients has been rarely reported. It is not certain whether the present findings should be regarded as selective preservation of a type of sleep pattern or whether there are special factors that enhance positive bursts in stage II or III coma of Reye's syndrome.

Visually evoked responses in multiple sclerosis.

Visually evoked cerebral responses (VERs) from the occipital and central areas were compared between 50 patients with multiple sclerosis and 50 control subjects. The average peak latencies of four occipital components (OII-OV) and two central ones (CIV and CV) were significantly delayed. In no instance was the amplitude significantly different. Routine EEGs were either entirely normal (16) or showed only minor findings (10) in 26 patients. Of this group, nine showed abnormal VERs. Seventeen patients had clinical symptoms or signs which pointed to spinal cord involvement only; nonetheless, eight in this group had abnormal responses. Inasmuch as changes in visually evoked potentials are not directly dependent upon the presence of a demonstrable field defect, the technique may be useful in detecting otherwise occult cerebral lesions.