A 3-week-old boy is brought to the emergency department due to lethargy for a day. The patient was breastfeeding well until this morning, when he became increasingly difficult to arouse. He was born full-term to a 35-year-old mother who had a spontaneous vaginal delivery at home. She took prenatal vitamins throughout pregnancy and received routine prenatal care. However, the boy did not receive any vaccinations or medications after birth due to parental preference for a "natural" newborn period. Family history is unremarkable. Head circumference is at the 99th percentile. Weight and length are at the 25th percentile. Physical examination shows a large, bulging anterior fontanel. The eyes appear driven downward and the patient is not able to track upward. No scalp swelling is present. Intracranial hemorrhage is confirmed on head CT scan. Which of the following is the most likely cause of this infant's condition?

Question

A 3-week-old boy is brought to the emergency department due to lethargy for a day.  The patient was breastfeeding well until this morning, when he became increasingly difficult to arouse.  He was born full-term to a 35-year-old mother who had a spontaneous vaginal delivery at home.  She took prenatal vitamins throughout pregnancy and received routine prenatal care.  However, the boy did not receive any vaccinations or medications after birth due to parental preference for a "natural" newborn period.  Family history is unremarkable.  Head circumference is at the 99th percentile.  Weight and length are at the 25th percentile.  Physical examination shows a large, bulging anterior fontanel.  The eyes appear driven downward and the patient is not able to track upward.  No scalp swelling is present.  Intracranial hemorrhage is confirmed on head CT scan.  Which of the following is the most likely cause of this infant's condition?

Quizplus · Accepted Answer

11ec160b_3b24_ee96_9249_75510048f811_MD0001_00 Vitamin K is an essential cofactor for gamma-glutamyl carboxylase, the enzyme responsible for converting glutamyl residues to gamma-carboxyglutamates. Carboxylation is critical for the function of clotting factors II (prothrombin), VII, IX, and X as it allows for the creation of calcium-binding sites. These sites attract the clotting factors to negatively charged phospholipids on platelets and endothelial cells, encouraging coagulation and thrombin formation. Healthy children and adults rarely need exogenous vitamin K supplementation as endogenous colonic bacterial flora generates vitamin K and leafy-green vegetables are rich in vitamin K. In contrast, newborns have low vitamin K stores due to poor transplacental transfer and low content in breast milk. Insufficient levels remain in the first month of life due to delayed production by the gradual colonization of bacterial gut flora as well as insufficient utilization by an immature liver. Neonatal vitamin K deficiency is prevented by administration of intramuscular vitamin K at birth. Without exogenous vitamin K, as in this patient, vitamin K deficiency results in impaired clotting factor carboxylation and, therefore, a propensity for bleeding. Intracranial hemorrhage (ICH) is a potentially fatal complication, often presenting with signs of increased intracranial pressure (eg, altered mental status, enlarging head circumference, bulging fontanel, downward-driven eyes). (Choice A) Abusive head trauma can lead to intracranial bleeding and subdural hemorrhage in infants. This is less likely in an infant with no external trauma signs and no prior vitamin K prophylaxis. If the infant had received a vitamin K injection at birth, abusive head trauma would be the most likely diagnosis. (Choice B) Neonatal bacterial meningitis can present with lethargy or irritability, but affected patients also have fever or hypothermia. In addition, bacterial meningitis does not typically cause ICH. (Choice C) ICH from birth injuries is most common in operative deliveries involving vacuum or forceps assistance. Infants with birth injuries are typically symptomatic shortly after birth rather than at age 1 month. (Choice D) Germinal matrix fragility is responsible for intraventricular hemorrhage in premature infants. The germinal matrix starts involuting around 28 weeks gestation and disappears by full term. Educational objective: Vitamin K deficiency results in impaired clotting factor carboxylation. Newborns are at risk for vitamin K deficiency due to poor transplacental transfer of vitamin K and low content in breast milk. All newborns should receive vitamin K prophylaxis to prevent bleeding complications. __________ References: Rise in late onset vitamin K deficiency bleeding in young infants because of omission or refusal of prophylaxis at birth. (http://www.ncbi.nlm.nih.gov/pubmed/24842255) Vitamin K deficiency bleeding: a case study. (http://www.ncbi.nlm.nih.gov/pubmed/24300958)

A 3-Week-Old Boy Is Brought to the Emergency Department Due