Severe achondroplasia with developmental delay and acanthosis nigricans

Severe Achondroplasia with Developmental Delay and Acanthosis Nigricans

Severe Achondroplasia with Developmental Delay and Acanthosis Nigricans (SADDAN) is a rare genetic disorder characterized by severe skeletal abnormalities, developmental delay, and a skin condition called acanthosis nigricans. It is caused by mutations in the FGFR3 gene.

Symptoms

Individuals with SADDAN typically have severe short stature due to abnormal bone growth. The limbs are disproportionately short compared to the trunk, and there may be other skeletal abnormalities such as bowed legs and a prominent forehead. Developmental delay is common, with affected individuals experiencing delays in reaching developmental milestones such as sitting, crawling, and walking.

A distinguishing feature of SADDAN is the presence of acanthosis nigricans, a skin condition characterized by dark, thickened, and velvety patches of skin. These patches typically appear in body folds, such as the neck, armpits, and groin. Acanthosis nigricans can also occur in individuals without SADDAN, but its presence in combination with severe achondroplasia and developmental delay is highly suggestive of SADDAN.

Genetics

SADDAN is caused by mutations in the FGFR3 gene, which provides instructions for making a protein involved in the development and maintenance of bone and other tissues. The specific mutations associated with SADDAN result in an overactive FGFR3 protein, leading to abnormal bone growth and the other characteristic features of the disorder.

Diagnosis

Diagnosis of SADDAN is typically based on clinical features, including severe achondroplasia, developmental delay, and acanthosis nigricans. Genetic testing can confirm the presence of mutations in the FGFR3 gene, further supporting the diagnosis.

Treatment

There is currently no cure for SADDAN, and treatment is focused on managing the symptoms and providing supportive care. This may include physical therapy to help with mobility and development, as well as regular monitoring of growth and development.

Prognosis

The prognosis for individuals with SADDAN can vary depending on the severity of the symptoms. Some individuals may have significant developmental delays and require ongoing support and care. However, with appropriate management and support, many individuals with SADDAN can lead fulfilling lives.