Blount Disease, Infantile

Description

Blount disease is a developmental condition characterized by disordered endochondral ossification of the medial part of the proximal tibial physis resulting in multiplanar deformities of the lower limb (review by Sabharwal, 2009).

Clinical Features

Blount (1937) described 22 cases of bowlegs in infants, with progressive deformity and radiologic findings of sloping proximal tibial epiphysis and a medial beak of the metaphysis. Blount (1937) suggested the existence of an infantile type with onset in the first year or two of life and an adolescent type developing just before puberty (see 259200).

Bathfield and Beighton (1978) noted a predilection for blacks.

Duncan et al. (1983) reviewed the literature emphasizing the higher frequency in blacks than in whites, the higher frequency of the infantile form than the adolescent form, and the higher frequency of bilateral involvement than unilateral involvement.

Inheritance

Blount disease is probably a multifactorial disorder with genetic, humoral, biomechanical, and environmental factors (Sabharwal, 2009).

Although Bathfield and Beighton (1978) found a modest familial aggregation, with bowlegs in 10 of 231 sibs and in 16 of the parents, multifactorial inheritance of the infantile form of Blount disease was espoused.

Sibert and Bray (1977) reported cases in infants in 4 generations and suggested autosomal dominant inheritance with incomplete penetrance. Duncan et al. (1983) referred briefly to a black family with affected members in 3 generations. McKusick (1986) observed a family of mixed African-European ancestry with 9 affected persons in 4 generations, with at least 1 instance of male-to-male transmission. The most severely affected, a male, was 76 inches tall.

Sevastikoglou and Eriksson (1967) observed 4 affected with the infantile form in a sibship of 6 children. Two of the affected were identical twins.

Ikegawa et al. (1990) described the disorder in identical twin boys who presented at the age of 1 year and 4 months with bilateral bowlegs. The family history was negative.