Differential Diagnosis of an Infant with Easy Bleeding, Bruising

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ACEP Now: September 2025

A more recent prospective five-year study also showed that late VKDB can extend all the way up to five months of age. The study identified 47 infants with late VKDB.² The mean age of onset was 10.5 ± 5.75 weeks, with a range of 2-21 weeks of age. This study identified infants with late VKDB all the way up through five months of age. Most deliveries were at home (55 percent) and 83 percent of infants were exclusively breastfed. Like the prior study, 23 percent of infants with late VKDB died and intracranial hemorrhage occurred in 32 percent of all infants with late VKDB.

What about later than five months of age? There is an older five-year retrospective nationwide survey in Japan of late VKDB that evaluated children from 1981-1985.⁴ The study identified 543 cases of VDKB in infants older than 2 weeks—meaning late VKDB. Of these cases, 427 cases were considered idiopathic, and 57 cases were considered “secondary” to other causes such as obvious hepatobiliary lesions, chronic diarrhea, long-term antibiotic therapy, etc.

In those cases of idiopathic late VKDB that occurred after two weeks, 269 cases (63 percent) occurred during the first and second month of age and 90 percent of infants were entirely breastfed alone. Twenty-three cases occurred between two to three months, 11 cases between three to four months, six cases between four to five months, one case between five to six months, and even a single case all the way out to seven to eight months. Although this outlier of seven to eight months is extremely rare in the medical literature in our search, this study does suggest that we should seriously consider late VKBD through at least six months of age as a cause of easy bleeding and bruising—particularly in solely breastfed infants.

Yet another retrospective study had a single child with late VKDB at 24 weeks (6 months) of age.⁵ And like the other studies, late VKDB was highly associated with intracranial bleeding (58 percent) with a mortality of 19 percent.

Summary

Late VKDB can occur up to six months after birth, particularly in babies who are solely breastfed. Asking about vitamin K administration after birth is extremely important in infants younger than 6 months with easy bleeding or easy bruising or any clinical circumstance that could be caused by life-threatening bleeding such as intracranial hemorrhage.

Dr. Jones is associate professor at the department of emergency medicine & pediatrics and the program director of pediatric emergency medicine fellowship at the University of Kentucky in Lexington, Kentucky.