This does not look like a disease to me. It looks like leaf scorch. Marginal necrosis, the browning of the edges of the leaves, is the hallmark sign. This can be caused by sun and heat stress. It usually occurs when there here is not enough water reaching the leaf margin to keep up with the transpiration process. It can frequently happen when a tree is in a place where there is reflected heat, like a driveway, fence, or the side of a building.  So the fact that the interior leaves are also affected makes sense.  Japanese maple are very fragile early in the season, and most do better in dappled light because of that.  The first leaves that come out on my Alaskan Sunset maple usually end up really crispy after the first week of hot weather.   Luckily, on the west side of the Cascades we usually have a few weeks of cool weather to let more leaves come in that can stand up to heat and sun stress. I just checked the weather history for the past couple weeks--it's been really hot there.  I believe leaf scorch is the diagnosis.  Here is what WSU's Hortsense recommends:

• Irrigate during dry periods. Wet the entire root zone, but do not overwater.
• Do not overfertilize.
• Avoid injury to roots and trunk.
• Soil compaction, which may be caused by heavy foot traffic or construction equipment, can prevent roots from taking up water, resulting in scorch symptoms.
• Do not plant trees against the sunny sides of buildings or pave over the roots of established trees.

http://hortsense.cahnrs.wsu.edu/Search/MainMenuWithFactSheet.aspx?CategoryId=1&SubCatId=5&PlantDefId=23&ProblemId=444