Physicians report success in a small study of a modified skin biopsy that hastens the earlier diagnosis of an inherited and progressively fatal nerve disease and seems to offer a clearer view of the disorder’s severity and progression. With a quicker and less invasive way to visualize the hallmark protein clumps of the rare but lethal disease — familial transthyretin amyloidosis — the researchers say they hope to more rapidly advance clinical trials of treatments that may slow the disease and extend patients’ lives.