Acromesomelic dysplasia, Grebe type

Acromesomelic dysplasia, Grebe type (also known as Grebe chondrodysplasia or Brazilian achondrodysplasia) is a rare, severe skeletal disorder characterized by marked shortening and malformation of the limbs, particularly affecting the middle (mesomelic) and distal (acromelic) segments. The condition follows a characteristic proximal-to-distal gradient of severity, meaning the hands and feet are more severely affected than the forearms and lower legs, which in turn are more affected than the upper arms and thighs. The hands and feet may show extremely short, malformed digits (brachydactyly) or even rudimentary, ball-shaped digits with fusion of finger and toe bones (synostosis). The long bones of the limbs are shortened and often bowed, while the axial skeleton (spine and trunk) is relatively spared, resulting in a disproportionately short-limbed stature. This condition is caused by homozygous or compound heterozygous mutations in the GDF5 gene (also known as CDMP1), which encodes growth/differentiation factor 5, a member of the bone morphogenetic protein family critical for cartilage and bone development. The GDF5 protein plays an essential role in limb morphogenesis and joint formation. Loss-of-function mutations in this gene disrupt normal skeletal patterning, particularly in the appendicular skeleton. The condition was first described in a large consanguineous family in Brazil by Grebe in 1952. There is currently no cure or disease-specific treatment for Grebe type acromesomelic dysplasia. Management is supportive and symptomatic, focusing on orthopedic interventions to address limb deformities and improve mobility, physical therapy, and adaptive devices to assist with daily activities. Genetic counseling is recommended for affected families. Intelligence and life expectancy are typically normal. Early diagnosis can be made prenatally or at birth based on clinical and radiographic findings, and molecular genetic testing of the GDF5 gene can confirm the diagnosis.

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