"Channelopathies are diseases caused by disturbed function of ion channel subunits or the proteins that regulate them". They may be congenital (from a mutation/s in the encoding gene) or acquired (from e.g. an "autoimmune attack on an ion channel"). There are a large number of clinical abnormalities known to be caused by channelopathies; many more presently under investigation. The SCN4A (called "sodium channel, voltage gated, type IV alpha subunit) belongs to the family of genes which transport sodium ions into cells and are found in skeletal muscle.

Mutations of the SCN4A gene (located on the long arm of chromosome 17 at position 23.3) causes several skeletal muscle abnormalities (e.g. hyper and hypokalemic periodic paralysis, paramyotonia congenita, potassium aggravated myotonia, one form of myasthenia gravis, etc). Variability in clinical presentation (phenotypic heterogeneity) may be confusing because of overlapping presentations in childhood. Treatment for some conditions exist.

Pediatric Neurology 

A study of 58 patients with HLHS and 44 non-HLHS patients with single ventricle physiology surviving >10 years indicates that HLHS survivors have  greatly reduced exercise tolerance, more educational issues (41% vs. 23%), & increased behavioral abnormalities (autism or ADHD) (12% vs. 0%) requiring greater multidisciplinary team involvement.

Archives of Diseases in Childhood 

"Milk production is under the influence of autocrine control" - with a rate of synthesis decreasing as the breast fills with milk. It has been assumed that milk ejection occurs in all alveoli simultaneously; though animal studies indicate that full alveoli eject milk earlier than less filled ones.

A study using ultrasound videos of milk duct flow during pumping indicates that flow from the two separate main milk ducts differ substantially (by 2-8 seconds) and the timing of myoepithelial cell response differs resulting in heterogeneity of alveolar milk emptying.

Journal of Human lactation