Chitobiase

Chitobiase is a rare genetic disorder characterized by the absence of the enzyme chitobiase, which is responsible for breaking down certain types of glycosaminoglycans (GAGs) in the body. This deficiency leads to the accumulation of these GAGs in various tissues, primarily affecting the skin, joints, and internal organs.

The primary symptom of chitobiase deficiency is a progressive skin disorder known as chitobiase deficiency disease (CDD). Individuals with CDD typically present with thickened, hyperkeratotic skin, often described as having a "fish scale" appearance. This skin condition can be painful and may lead to secondary infections. The severity of the skin involvement can vary widely among affected individuals.

Joint involvement is another key feature of chitobiase deficiency. Affected individuals may experience joint pain, stiffness, and swelling, which can progress to joint deformities and limited mobility over time. The exact mechanism by which GAG accumulation leads to joint damage is not fully understood, but it is believed to involve inflammation and tissue degeneration.

Internal organ involvement can also occur, although it is less common than skin and joint involvement. Affected individuals may experience liver disease, kidney disease, or other systemic complications.

Chitobiase deficiency is inherited in an autosomal recessive manner, meaning that an individual must inherit two copies of the defective gene, one from each parent, to be affected. The condition is caused by mutations in the CHIT1 gene, which encodes the chitobiase enzyme.

Diagnosis of chitobiase deficiency typically involves genetic testing to identify mutations in the CHIT1 gene. Treatment options are limited, and management focuses on symptom relief and supportive care. Skin care, physical therapy, and medications to manage pain and inflammation are commonly employed. Research into potential enzyme replacement therapies and other treatment strategies is ongoing.

The prognosis for individuals with chitobiase deficiency varies depending on the severity of organ involvement. Early diagnosis and management can improve outcomes, but the long-term prognosis is generally poor due to the progressive nature of the disease.