Review Question - QID 218720

Adolescent Blount disease is defined as idiopathic proximal tibia vara, with obesity being a known causative factor and hypertension being an often overlooked and under-treated associated entity in the pediatric population.

Unlike infantile Blount's, the adolescent form represents pathologic genu varum that occurs most commonly > 10 years of age with obesity and African-American descent being causative risk factors. The adolescent form is also typically less common, less severe, and more frequently unilateral. It is thought to be caused by idiopathic dyschondrosis of the proximal medial tibial physis, though the true etiology is likely multifactorial and related to mechanical overload in genetically susceptible individuals. The prevalence of vitamin D deficiency is similar to that of healthy children, but there is a significant association with hypertension, which is often undiagnosed and untreated and represents an important, potentially modifiable risk factor.

Lisenda et al. reviewed Vitamin D status in Blount disease. The authors recruited 50 patients with a mean age of 10.4 years preoperatively and postoperatively with Blount disease and screened them for calcium, phosphate, alkaline phosphatase, parathyroid, and 25-hydroxyvitamin D (25(OH)D) hormones. They found and concluded that the prevalence of Vitamin D deficiency in children with Blount disease was similar to that of healthy children and that there is no evidence that vitamin D deficiency is a factor in causing Blount disease.

Taussig et al. reviewed the prevalence of hypertension in pediatric tibia vara and slipped capital femoral epiphysis. The authors obtained blood pressure measurements in 44 patients with tibia vara and 127 patients with SCFE. They found that the prevalence of prehypertension/hypertension was significantly higher in the tibia vara (64%) and SCFE cohort (64%) compared with respective controls (43%). They concluded that patients diagnosed with either SCFE or tibia vara have a 2.5-fold higher odds of having high blood pressure compared with age-matched and sex-matched obese patients without bone disease.

Figures A and B represent full-length bilateral standing and AP knee radiographs, respectively, that demonstrate a dyschondrosis of the left proximal medial tibial physis and subsequent pathologic, unilateral genu varum.

Incorrect Answers:
Answer 2: Congenital hypothyroidism typically presents much earlier than 10 years of age and does not involve unilateral pathologic genu varum.
Answer 3: Metabolic syndrome represents a collection of abnormalities, namely high blood pressure, high blood sugar, excess body fat around the waist, and abnormal cholesterol levels. The patient has normal A1c and fasting triglyceride levels.
Answer 4: Primary varus gonarthrosis would not be expected in a 10-year-old child.
Answer 5: Vitamin D deficiency causes Rickets, which is associated with severe bilateral femoral and tibial bowing.