ATP6AP2
Name of Disorder

ATP6AP2-congenital disorder of glycosylation (ATP6AP2-CDG, also known as congenital disorder of glycosylation type IIr)

Symptoms

ATP6AP2-CDG is very rare X-linked disorder that affect primarily males. Only few patients are reported in the medical literature. Signs and symptoms develop during early infancy. Affected individuals may have variable degree of liver dysfunction. Impairment of immune system is associated with recurrent infections. Neurological abnormalities include intellectual disability (mild) and ataxia. Loose skin (cutis laxa) has been observed but improve with age. Individuals with ATP6AP2-CDG may have abnormal difference in facial features (dysmorphism).

Laboratory abnormalities include elevated liver enzymes, abnormal activities of coagulation factors, high blood cholesterol and low copper level.

Diagnosis

Common screening test relies on testing the appropriate glycosylation of common proteins (one commonly used glycoprotein is transferrin). This can be tested by different methods in blood. The ultimate diagnosis is genetic testing in blood. Individuals with ATP6AP2-CDG have one faulty copy of the ATP6AP1 gene, which is located on the X chromosome.

Treatment and prognosis

There are no specific treatments for ATP6AP2-CDG. Regular immunoglobulin infusions can be used for immunological abnormalities. Other treatments should be directed to treat symptoms and prevent complications. Given the rarity of ATP6AP2-CDG, there is no clear prognosis. The oldest reported patient 21 years old.