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Leukocyte adhesion deficiency type II
Leukocyte adhesion deficiency type II (LAD-II) is a form of LAD (see this term) characterized by recurrent bacterial infections, severe growth delay and severe intellectual deficit.
LAD-II is extremely rare: less than 10 cases have been reported so far.
The first signs usually occur in infancy or early childhood. Patients present recurrent bacterial infections, severe growth delay resulting in short stature, and severe intellectual deficit. Patients have the Bombay phenotype (they do not express the H antigen). Facial dysmorphism is common, characterized mainly by a depressed nasal bridge. Severe periodontitis is often present later in life and leads to early tooth loss. In adulthood, intellectual deficit and growth retardation, rather than infections, dominate the clinical picture.
LAD-II is a carbohydrate-deficient glycoprotein syndrome (CDG syndrome; see this term) and is therefore also referred to as CDG IIc. It results from mutations in the SLC35C1 gene (11p11.2), encoding the guanosine 5'-diphosphate (GDP)-fucose transporter localized in the Golgi apparatus. This is a specific fucose transporter that translocates GDP-fucose from the cytosol to the Golgi where it is used as a substrate for fucosylation.
Diagnosis is based on clinical findings and complete blood counts revealing leukocytosis with neutrophilia. Blood typing is essential to look for the Bombay blood group, which is present in all patients with LAD-II and is extremely rare in the general population. Final diagnosis is based on genetic analysis.
There is no differential diagnosis as the clinical symptoms of recurrent infections, leukocytosis, the Bombay blood group, and severe growth and intellectual deficit are unique to LAD-II.
Antenatal diagnosis through biochemical or molecular analysis of chorionic villus cells or amniocytes is possible in families for which the mutation has been identified.
Transmission is autosomal recessive.
Management and treatment
Management should focus on controlling infections and includes antibiotics. Fucose replacement may improve phagocytic function in some cases.
Infections in LAD-II are rarely life-threatening and thus patients may live to adulthood.
- Clinical genetics review
- English (2017)