Thank you Anne for your question to "Ask Extension".  My first question is are the symptoms spreading?  If they are not spreading then it could be freeze damage from this past winter.  If it is spreading then there are a couple of diseases to look at.              The first to look at is Volutella blight.  Branches die back and leaves turn from green to light green-yellow and finally to shades of tan. Affected leaves turn up and lie close to the stem. Black streaks may be found on some petioles or on stems near petiole attachment. These symptoms are similar to winter injury, except that numerous, small, salmon-pink fungal spore-producing structures (sporodochia) appear on lower surfaces of affected leaves and branches. Diseased branches should be pruned out when the foliage is dry.  An important measure to help prevent and control Volutella is thinning (instead of shearing) boxwood to improve air circulation and light penetration. Thinning is a type of pruning that removes interior stems.  Old fallen leaves and diseased leaves that have accumulated in the crotches of branches in the interior of the plant should be shaken out and removed.
     The other possibility is phytophthora crown and root rot. It is a fungal infection. Infected plants often show wilting, discolored or dead leaves which remain on the branches, dead twigs and branches, stunting, gradual decline, and premature plant death. Infected roots become watersoaked and rot. Streaking or dark staining may be observed when cuts are made into the wood near the crown of the plant, or cankers may be present on the crown. The fungus persists in the soil and in diseased plant material. Phytophthora prefers high soil moisture.  Do not replant boxwood in areas where it has died previously.  Remove and destroy infected plants, including roots where possible.  Your photo best matches this diagnosis.  There are no chemical controls.
     I hope that you find this information useful and if you have additional questions you are welcome to respond.

Hello Kevin,