Zimmermann-Laband syndrome

Zimmermann-Laband syndrome is an extremely rare, autosomal dominant congenital disorder. The name covers two conditions, type 1 and type 2, that share similar clinical features. The term was coined by Carl Jacob Witkop in 1971. Typical features are overgrowth of the gums (gingival fibromatosis), underdevelopment of the end bones of the fingers and toes, abnormal nails, loose joints and sometimes an enlarged liver and spleen. The nose and ears are usually large and poorly formed, which gives affected people a characteristic facial appearance, and intellectual disability may also be present. Gum overgrowth is usually present at birth or soon after, and males and females are equally affected. Type 1 is caused by pathogenic variants in KCNH1, a potassium channel gene, and variants in the same gene cause Temple-Baraitser syndrome, which has led many to think the two are one disorder. Type 2 is caused by variants in ATP6V1B2, which encodes the brain form of a proton pump subunit. Because the pattern is autosomal dominant, a person with the condition has a 50 percent chance of passing it to each child. There is no known cure. Care centres on yearly checks of growth and development, physiotherapy, occupational therapy and speech therapy, with anticonvulsants when epilepsy is present.