GAPO syndrome

GAPO syndrome is an extremely rare autosomal recessive genetic disorder whose name is an acronym derived from its four cardinal features: Growth retardation, Alopecia (hair loss), Pseudoanodontia (failure of tooth eruption despite the presence of tooth buds), and Optic atrophy. The condition is caused by biallelic pathogenic variants in the ANTXR1 gene (also known as TEM8), which encodes a transmembrane protein involved in extracellular matrix homeostasis. The underlying pathology involves progressive accumulation of extracellular matrix material in various tissues, leading to the multisystem manifestations of the disease. Affected individuals typically present in infancy or early childhood with severe growth failure, complete or near-complete absence of scalp hair, eyebrows, and eyelashes, and failure of both primary and permanent teeth to erupt through the gums. Optic atrophy, which can lead to progressive visual impairment, is another hallmark feature. Additional clinical findings may include thickened calvaria (skull bones), frontal bossing, a prominent forehead, depressed nasal bridge, thick lips, and skin changes including premature aging of the skin. Some patients develop hepatomegaly, and connective tissue abnormalities may affect the cardiovascular system. There is currently no curative treatment for GAPO syndrome. Management is supportive and multidisciplinary, involving dental prostheses to address the absence of erupted teeth, ophthalmologic monitoring and intervention for optic atrophy, growth hormone evaluation, and dermatologic care. Regular monitoring of organ systems, particularly the eyes and cardiovascular system, is recommended. Genetic counseling is important for affected families. Fewer than 50 cases have been reported in the medical literature worldwide, with a notable cluster of cases described in Turkish and Brazilian populations.

Common questions about GAPO syndrome