A 9-week-old Caucasian infant is brought to the primary care physician for evaluation of purpura and petechiae. His parents noted the bruising the previous night, which grew progressively worse throughout the next day. The lesions seemed to appear "out of the blue" without apparent cause, including trauma. The child had no fever, cough, or vomiting. He had been alert and was feeding well.
The child was born at term via cesarean delivery because of a maternal history of herpes simplex virus infection. The pregnancy was otherwise uncomplicated. The child weighed 6 lb 12 oz at birth. Prophylactic vitamin K was given before circumcision, which was done in the newborn nursery without bleeding or oozing.
The postnatal period was significant for mild jaundice, which developed when the infant was 3 days old. He did not require phototherapy. When the infant was about 4 weeks of age, colicky symptoms developed, along with increased spitting up.
A maternal uncle had experienced excessive bleeding during tooth extraction that required vitamin K therapy. There was no other family history to indicate a possible bleeding diathesis (including menorrhagia, easy bruising, postoperative bleeding, or early hysterectomy).
Physical examination revealed an alert infant in no distress with normal vital signs. Weight was at the 50th percentile. There was a dime-sized bluish bruise below the umbilicus and pinpoint blue bruising above the umbilicus. In addition, bluish bruising was present on the left anterior thigh, left flank, right posterior arm and shoulder, and temples bilaterally. Bleeding was absent from the nose, gums, and other mucous membranes. The infant had normal skin texture and elasticity. Joint mobility was normal. The remainder of the physical examination was unremarkable.
The child was hospitalized with a diagnosis of unexplained purpura. Given the family history, a bleeding diathesis was suspected. However, the complete blood cell count was normal, with no left shift.
Is the workup for bleeding disorders sufficient in this case--or is further investigation for other underlying conditions needed?