What is the likely diagnosis for an 11-month-old African American baby with wide anterior fontanel, costochondral joint prominence, and genu varum?

The symptoms described in the scenario—wide anterior fontanel, costochondral joint prominence, and genu varum—are classic indicators of rickets, particularly in the context of vitamin D deficiency. Rickets primarily affects bone development in children, leading to softening and weakening of the bones due to inadequate mineralization, often due to insufficient levels of vitamin D, calcium, or phosphate.

The wide anterior fontanel can result from delayed closure associated with skeletal abnormalities seen in rickets. Costochondral joint prominence, sometimes referred to as "rachitic rosary," occurs as a result of the improper mineralization of growing bones, leading to abnormal growth patterns. Genu varum, or bow-leggedness, is another common manifestation in young children with rickets due to the weakening of the long bones, leading to abnormal curvature.

In this case, given the age of the child, the presentation aligns well with nutritional rickets, which is prevalent in various populations, particularly where dietary intake of vitamin D is insufficient. This diagnosis underscores the importance of vitamin D in bone health during childhood, emphasizing the need for adequate nutrition and monitoring in young children.