Secondary gleno-humeral joint dysplasia in children with persistent obstetric brachial plexus palsy

The study aimed to evaluate the degree of gleno-humeral joint deformation in children with persistent obstetric brachial plexus palsy and its effect on limb function. Computer tomography was performed in 24 children in the mean age of 6.1 years. There were eight boys and 16 girls. Gleno-scapular angle, congruency of gleno-humeral joint and joint deformity according to Waters at all. criteria were measured. The mean functional score according to the Mallet classification system was 12.3 points. The joint was stabile in nine, subluxed in seven and dislocated in nine cases. Gleno-scapular angle in affected joints was 23.3° and in non-affected 4.5°. The glenoid was statistically more retroverted in older children. With more severe posterior incongruence there was statistically greater limitation of passive external rotation, active internal rotation and a poorer functional result according to Mallet. Abnormalities were found also in the humeral head, being deformed and smaller compared to the non-affected side in all cases. Glenoid retroversion, posterior subluxation/dislocation of humeral head and smaller humeral head size are the abnormalities, most often identified in CT examinations. Shoulder function and in particular, passive, external rotation are closely associated with the degree of deformity of the glenoid, as well as with the extent of posterior humeral head dislocation

Mechanisms of Disease: the kidney-specific chloride channels ClCKA and ClCKB, the Barttin subunit, and their clinical relevance

Rodent ClC-K1 and ClC-K2, and their respective human orthologs ClCKA and ClCKB, are chloride channels specific to the kidney (and inner ear); Barttin is their functionally important subunit. ClC-K1 is predominantly localized to the thin ascending limb of the loop of Henle. ClC-K2 is expressed more broadly in the distal nephron; expression levels are highest along the thick ascending limb of the loop of Henle and distal convoluted tubule. Expression of ClC-K1 is upregulated by dehydration and downregulated by the diuretic furosemide, whereas expression of ClC-K2 is upregulated by furosemide and downregulated by high salt levels. ClCKA is important for maintenance of the corticomedullary osmotic gradient and the kidney's capacity to concentrate urine. If its ortholog, ClC-K1, is nonfunctional in mice, renal diabetes insipidus develops. ClCKB is a key determinant of tubular reabsorption of chloride and electrolytes along the distal tubule. A severe salt-losing tubulopathy (Bartter syndrome type III) develops if ClCKB is nonfunctional, whereas a common genetic variant of the CLCNKB gene that leads to increased activity of ClCKB results in salt-dependent hypertension. Disruption of the gene encoding Barttin, BSND, results in a 'double knockout' of the functions of both ClCKA and ClCKB, manifesting as Bartter syndrome type IV with sensorineural deafness and an especially severe salt-losing phenotype