What is the most likely cause of a medial metaphyseal corner fracture of the distal femur in a 13-month-old boy with a history of leg pain, irritability, and refusal to stand, and physical examination findings of mild swelling and point tenderness in the left distal thigh?

Differential Diagnosis for the 13-month-old Boy with Leg Pain

The patient's presentation with a medial metaphyseal corner fracture of the distal femur, along with other clinical findings, suggests several potential diagnoses. These can be categorized as follows:

• Single Most Likely Diagnosis

  • A. Child Abuse: The presence of a specific type of fracture (medial metaphyseal corner fracture) that is highly suggestive of non-accidental trauma, combined with the patient's irritable behavior and refusal to stand, points towards child abuse as the most likely cause. The lack of a clear accidental trauma history and the presence of other signs such as point tenderness and swelling further support this diagnosis.

• Other Likely Diagnoses

  • E. Rickets: Although less likely than child abuse given the specific fracture type, rickets could be considered due to the patient's low weight percentile, lack of routine healthcare, and exclusive breastfeeding without vitamin D supplementation until age 6 months. Rickets can cause bone softening and increase the risk of fractures.
  • D. Osteogenesis Imperfecta: This genetic disorder leads to fragile bones and could explain the fracture. However, it would typically be associated with a family history of fractures or blue sclerae, and the patient's mother had fractures as a child, which might suggest a familial component.

• Do Not Miss Diagnoses

  • B. Congenital Syphilis: Although less common, congenital syphilis can cause metaphyseal fractures and should be considered, especially given the lack of prenatal care and the presence of beefy erythematous plaques with satellite papules, which could be indicative of a congenital infection. Missing this diagnosis could have significant long-term consequences.
  • C. Langerhans Cell Histiocytosis: This rare condition can cause bone lesions and fractures. While it's less likely, it's crucial not to miss it due to its potential for severe outcomes if left untreated.

• Rare Diagnoses

  • Other rare bone disorders or metabolic conditions could potentially explain the patient's presentation but are less likely given the information provided. These might include conditions affecting bone mineralization or rare genetic syndromes associated with bone fragility or fractures.