Pathogenic variants in SQOR encoding sulfide:quinone oxidoreductase are a potentially treatable cause of Leigh disease

Hydrogen sulfide, a signaling molecule formed mainly from cysteine, is catabolized by sulfide:quinone oxidoreductase (gene SQOR). Toxic hydrogen sulfide exposure inhibits complex IV. We describe children of two families with pathogenic variants in SQOR. Exome sequencing identified variants; SQOR enzyme activity was measured spectrophotometrically, protein levels evaluated by western blotting, and mitochondrial function was assayed. In family A, following a brief illness, a 4-year-old girl presented comatose with lactic acidosis and multiorgan failure. After stabilization, she remained comatose, hypotonic, had neurostorming episodes, elevated lactate, and Leigh-like lesions on brain imaging. She died shortly after. Her 8-year-old sister presented with a rapidly fatal episode of coma with lactic acidosis, and lesions in the basal ganglia and left cortex. Muscle and liver tissue had isolated decreased complex IV activity, but normal complex IV protein levels and complex formation. Both patients were homozygous for c.637G > A, which we identified as a founder mutation in the Lehrerleut Hutterite with a carrier frequency of 1 in 13. The resulting p.Glu213Lys change disrupts hydrogen bonding with neighboring residues, resulting in severely reduced SQOR protein and enzyme activity, whereas sulfide generating enzyme levels were unchanged. In family B, a boy had episodes of encephalopathy and basal ganglia lesions. He was homozygous for c.446delT and had severely reduced fibroblast SQOR enzyme activity and protein levels. SQOR dysfunction can result in hydrogen sulfide accumulation, which, consistent with its known toxicity, inhibits complex IV resulting in energy failure. In conclusion, SQOR deficiency represents a new, potentially treatable, cause of Leigh disease.

Stereotactic CT-guided brain biopsy in the dog

This study evaluated the accuracy of a new stereotactic CT-guided brain biopsy (SCTGBB) device on 23 client-owned dogs which presented with a brain lesion. Biopsy of the lesion was achieved in 95 per cent of cases. The target tissue was not sampled in one dog. Complications were observed in six dogs. Two dogs with highly vascularised brainstem tumours died after SCTGBB. Minor complications (slight variation in the neurological status) were observed in a further four cases. A diagnosis was reached in 16 dogs after cytological examination and in 21 dogs after histological evaluation. SCTGBB is an accurate diagnostic method for the diagnosis of brain lesions.

PCR analysis and spatial repartition of trypanosomes infecting tsetse flies in Sidéradougou area of Burkina Faso

A parasitological and entomological survey was conducted in the Sideradougou area (south of Bobo Dioulasso, Burkina Faso) in order to identify transmission factors of African trypanosomosis. A total of 3600 tsetse flies (Glossina tachinoides, Glossina palpalis gambiensis) were captured along 120 km of linear gallery forest and half of them were dissected. PCR analysis was undertaken on parasitologically positive flies (161 G. tachinoides, 92 G. palpalis gambiensis) to characterize the different trypanosomes. All the results were integrated in a GIS (Geographical Information System). Spatial repartition of the characterized trypanosomes enabled to recognize different areas with specific patterns of infection. Relations with environmental factors are discussed.