A 5 year old male child presents with continuous bleeding from mouth. He had h/o fall early in the morning while playing. No h/o bruising or hematoma. He is taking amoxycillin for his middle ear infection. O/E he is stable and there is a small laceration in the lower lip with oozing of blood. Hb 12.8g%, hematocrit 35.4%, WBC count 8400/mm3, Platelets 300 X 109/L- Prothrombin time 11.5 seconds, aPTT 37.2 seconds. Diagnosis

**Core Concept**
The child presents with continuous bleeding from the mouth, suggesting a possible coagulopathy. The presence of a small laceration and stable vital signs indicates a localized bleeding issue, but the prolonged prothrombin time (PT) and normal activated partial thromboplastin time (aPTT) suggest a problem with the extrinsic coagulation pathway.

**Why the Correct Answer is Right**
The prolonged PT indicates a deficiency in the extrinsic pathway, which involves factors VII, X, V, prothrombin (II), and fibrinogen. In this case, the child is taking amoxicillin, which is a penicillin antibiotic that can affect the production of vitamin K-dependent clotting factors, such as factors II, VII, IX, and X. This is because the bacteria that produce vitamin K-dependent clotting factors are inhibited by amoxicillin, leading to a decrease in these clotting factors and a subsequent prolongation of PT.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the normal aPTT suggests that the intrinsic pathway, which involves factors XII, XI, IX, VIII, X, V, and prothrombin, is not affected. The normal aPTT also suggests that the child does not have a deficiency in factors VIII, IX, or XI, which are involved in the intrinsic pathway.

**Option B:** This option is incorrect because the child's clinical presentation and laboratory results do not suggest a disorder of platelet function or a primary platelet disorder. The platelet count is normal, and the bleeding is not excessive for the size of the laceration.

**Option C:** This option is incorrect because the normal aPTT and PT suggest that the child does not have a deficiency in factors VIII, IX, XI, or XII, which are involved in the intrinsic pathway. The normal platelet count also suggests that the child does not have a primary platelet disorder.

**Option D:** This option is incorrect because the child's clinical presentation and laboratory results do not suggest a disorder of fibrinogen or a primary fibrinogen disorder. The PT is prolonged, but the aPTT is normal, suggesting that the problem lies in the extrinsic pathway, not the fibrinogen pathway.

**Clinical Pearl / High-Yield Fact**
When a child presents with bleeding and is taking antibiotics, consider the possibility of vitamin K-dependent clotting factor deficiency due to antibiotic-induced inhibition of bacteria that produce these factors. This is a classic exam trap that can be easily missed.

**Correct Answer:** B.

✓ Correct Answer: B. Von Willebrand disease