Nemaline myopathy caused by mutations in the muscle alpha-skeletal-actin gene.

Nemaline myopathy (NM) is a clinically and genetically heterogeneous disorder characterized by muscle weakness and the presence of nemaline bodies (rods) in skeletal muscle. Disease-causing mutations have been reported in five genes, each encoding a protein component of the sarcomeric thin filament. Recently, we identified mutations in the muscle alpha-skeletal-actin gene (ACTA1) in a subset of patients with NM. In the present study, we evaluated a new series of 35 patients with NM. We identified five novel missense mutations in ACTA1, which suggested that mutations in muscle alpha-skeletal actin account for the disease in approximately 15% of patients with NM. The mutations appeared de novo and represent new dominant mutations. One proband subsequently had two affected children, a result consistent with autosomal dominant transmission. The seven patients exhibited marked clinical variability, ranging from severe congenital-onset weakness, with death from respiratory failure during the 1st year of life, to a mild childhood-onset myopathy, with survival into adulthood. There was marked variation in both age at onset and clinical severity in the three affected members of one family. Common pathological features included abnormal fiber type differentiation, glycogen accumulation, myofibrillar disruption, and "whorling" of actin thin filaments. The percentage of fibers with rods did not correlate with clinical severity; however, the severe, lethal phenotype was associated with both severe, generalized disorganization of sarcomeric structure and abnormal localization of sarcomeric actin. The marked variability, in clinical phenotype, among patients with different mutations in ACTA1 suggests that both the site of the mutation and the nature of the amino acid change have differential effects on thin-filament formation and protein-protein interactions. The intrafamilial variability suggests that alpha-actin genotype is not the sole determinant of phenotype.

Nevoid hypertrichosis with multiple patches of hair that underwent almost complete spontaneous resolution.

Four cases with multiple patches of nevoid hypertrichosis have been reported. This fifth patient had multiple patches of nevoid hypertrichosis that underwent almost complete spontaneous resolution. Areas of unaffected skin showed depigmentation that followed the lines of Blaschko.

Survival after neonatal myocardial infarction.

These are case reports of two children with structurally normal hearts and with normal coronary arteries, who survived myocardial infarction in the early neonatal period. They are only the third and fourth reported survivors of neonatal myocardial infarction and the first in which hypercholesterolemia is postulated to have played an important role. The most likely cause of the myocardial infarction was thrombosis or thromboembolism. Changes in hemostatic function associated with hypercholesterolemia may be relevant.

False negative results on newborn screening for cystic fibrosis.

Over a 5 year period in Newcastle, 18 new cases of cystic fibrosis (CF) were diagnosed in children who had been screened in the newborn period. In six of these children, the screening programme failed. Four of these children had a normal screen and an additional two had elevated immunoreactive trypsin (IRT), but there were problems with the notification procedure. Three of the children missed by the screening process had a significantly delayed diagnosis; in all three cases the diagnosis of CF was suspected clinically, but a sweat test was delayed because of false reassurance from the fact that the child had been screened for CF. In a fourth case, multiple elevated sweat electrolyte levels were obtained, but the diagnosis of CF was considered to be in doubt because of the normal IRT assay. A sweat test should be performed on any child in whom there is clinical suspicion of CF.