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.

Epidemiology

LAD-II is extremely rare: less than 10 cases have been reported so far.

Clinical description

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.

Etiology

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.

Diagnostic methods

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.

Differential diagnosis

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

Antenatal diagnosis through biochemical or molecular analysis of chorionic villus cells or amniocytes is possible in families for which the mutation has been identified.

Genetic counseling

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.

Prognosis

Infections in LAD-II are rarely life-threatening and thus patients may live to adulthood.