**Question:** The parents of a 13-month-old boy are contacted by a local social agency because the day care representative reported them for suspected child abuse based on "too many bruises." The parents deny the abuse and promptly arrange for their child to be seen by a medical specialist. The child has multiple large bruises on their legs, anus, and buttocks. No skin abrasions and no "pattern marks" are seen. PTT is prolonged and PT and bleeding time are normal. Which of the following is the most probable cause of the bruises?

A. Vitamin K deficiency
B. Hemophilia
C. Inherited platelet function disorder
D. Uncontrolled bleeding disorder

**Correct Answer:** C. Inherited platelet function disorder

**Core Concept:**

In this scenario, we are discussing a child with multiple large bruises without any skin abrasions or pattern marks, prolonged PTT, normal PT, and normal bleeding time. These findings suggest a bleeding disorder, as the prolonged PTT indicates impaired clotting factor VIII, which is consistent with a bleeding disorder.

**Why the Correct Answer is Right:**

The correct answer is Inherited platelet function disorder (option C) because this type of disorder results from a defect in platelet function, leading to impaired clotting factor VIII production and thereby affecting the normal clotting cascade. This results in excessive bleeding, as observed in the presented case.

**Why Other Options are Incorrect:**

A. Vitamin K deficiency (option A) is unlikely in this case, as the bleeding time and PT are normal, indicating that vitamin K synthesis and clotting factor VII production are not the issue.
B. Hemophilia (option B) is unlikely due to the normal clotting factor VIII level and normal bleeding time. Hemophilia is a condition where factor VIII levels are low, leading to excessive bleeding.
D. Uncontrolled bleeding disorder (option D) is also unlikely based on the normal bleeding time and PT. Uncontrolled bleeding disorders usually present with prolonged bleeding time.

**Clinical Pearl:**

In cases of unexplained multiple bruises in a child, inherited platelet function disorder should be considered in the differential diagnosis, especially when there are no pattern marks and normal coagulation parameters. This can help guide appropriate further diagnostic tests and treatment options, ultimately improving patient care.