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Rhizomelia is characterized by disproportionately short upper arms and thighs compared to the forearms, lower legs, and trunk.

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Typically symmetric
Evident at birth or in early infancy
Reflects abnormal endochondral ossification, particularly affecting the long bones

Limb Segment Terminology:

Limb Segment	Medical Term	Bones Involved
Proximal	Rhizomelia	Humerus, Femur
Middle	Mesomelia	Radius/Ulna, Tibia/Fibula
Distal	Acromelia	Hands, Feet
Entire limb	Micromelia	Generalized limb shortening

Etiology

Skeletal Dysplasias

Condition	Distinguishing Features
‣	Rhizomelia, frontal bossing, trident hands, lumbar lordosis
‣	Rhizomelia with joint laxity, normal facies
‣	Severe rhizomelia with micromelia, cloverleaf skull

Metabolic Disorders

Disorder	Notes
Rhizomelic ‣	Peroxisomal disorder with stippled epiphyses, cataracts
‣	Dysostosis multiplex with possible proximal shortening

Syndromic Associations

Syndrome	Notes
‣	Cholesterol synthesis defect; short limbs + syndactyly
‣	Facial dysmorphism, growth restriction, ± limb shortening

Clinical Features

Feature	Notes
Short upper limbs/thighs	Seen when arms/thighs are markedly shorter than forearms/shanks
Trunk relatively normal	In many skeletal dysplasias
May impair mobility	Depending on severity and underlying disorder
Joint hyperlaxity or stiffness	In certain dysplasias (e.g., pseudoachondroplasia)

Plain Radiographs