The term "dwarfism" describes many types of genetic mutations -- some inherited, some spontaneous mutations -- that result in short stature. Most cases fall into one of two types: short trunk but more normal limbs, or normal trunk but short limbs. In many cases, but not all, doctors can diagnose dwarfism at birth or even in utero, by looking at your baby's physical appearance or skeletal images. Certain metabolic or hormonal disorders cause proportionate dwarfism, which might not be evident at birth. The ease of diagnosis at birth depends on the type of dwarfism.
The most common type of dwarfism, achondroplasia, affects 1 in 15,000 to 40,000 babies, according to Kids Health. About 70 percent of little people have this type of dwarfism. Your doctor can generally diagnose achondroplasia at birth. Babies with this condition have a larger-than-normal head and forehead, a normal-size torso and shorter-than-normal arms and legs. While mutations in the FGFR3 gene cause this disorder, around 80 percent of people with achondroplasia develop the condition as a result of a spontaneous genetic mutation rather than inheriting it, according to Genetics Home Reference. If inherited, it's inherited as a dominant trait, meaning your child needs to inherit just one copy of the gene.
A baby with diastrophic dysplasia, another common form of dwarfism, occurring in about 1 in 100,000 births, according to Kids Health, can cause ear malformations or club feet, along with shortened forearms and calves. Around 50 percent of babies with this type of dwarfism have cleft palate, the Genetic Home Reference website reports. An abnormality in the SLC26A2 gene causes this type of dwarfism, which is usually evident at birth. Because it's inherited as a recessive disorder, both parents must carry a copy of the gene, although neither might have the disorder themselves.
A baby with spondyloepiphyseal dysplasia, which affects 1 in 95,000 infants, might also have clubfoot and cleft palate along with a barrel-chested appearance and decreased growth in the trunk and neck. This might not be evident until age 5, Kids Health explains. Hands and feet are usually normal-size. Genetically, most cases occur from spontaneous mutations in the COL2A1 gene, according to the Genetics Home Reference.
Children with dwarfism caused by hormonal or metabolic disorders have normally proportioned trunk and limbs, but decreased growth overall, so that they're smaller than normal. Your doctor might not diagnose some types of proportionate dwarfism, such as growth hormone deficiency, until around age 2 or 3, according to MedlinePlus. Hormone injections often, but not always, help your child reach a more normal height. Primordial dwarfism, a rare condition, results from growth delay early in fetal development; a baby born with this condition will be much smaller than normal, but proportionately so.