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Mesomelia refers to disproportionate shortening of the middle segments of the limbs—the radius and ulna (forearm) and the tibia and fibula (lower leg)—relative to the proximal (humerus/femur) and distal segments (hands/feet).

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It is most easily observed when the mid-limb appears recessed or sunken, giving the arms or legs a bowed or curved appearance.

Limb Segment Terminology

Segment	Term	Bones Involved
Proximal	Rhizomelia	Humerus, Femur
Middle	Mesomelia	Radius/Ulna, Tibia/Fibula
Distal	Acromelia	Hands, Feet
Entire Limb	Micromelia	All segments shortened

Clinical Features

Feature	Description
Short forearms/lower legs	Most visible when compared to upper arms or thighs
Wrist or ankle deformities	Due to abnormal bone development
Functional limitation	May include reduced range of motion or limb alignment issues
Disproportionate short stature	Body disproportionately short compared to trunk

Radiology

Plain Radiographs

Finding	Description
Short radius/ulna or tibia/fibula	Relative to humerus/femur
Curved or bowed shafts	May be associated with dysplasia or deformity
Epiphyseal anomalies	Particularly in dyschondrosteosis or chondrodysplasias
Delayed bone age	Seen in some endocrine/metabolic disorders

Etiology

A. Skeletal Dysplasias

Condition	Distinguishing Features
Léri-Weill dyschondrosteosis	Mesomelia + Madelung deformity; due to SHOX gene mutation
Mesomelic dysplasia	Includes Langer and Ellis types; severe mesomelia, dysplastic bones
Ellis-van Creveld syndrome	Mesomelia + polydactyly, short ribs, heart defects

B. Genetic Syndromes

Syndrome	Key Features
Turner syndrome	SHOX haploinsufficiency → mild mesomelia
Robinow syndrome	Mesomelia + genital hypoplasia + craniofacial anomalies
Down syndrome	Occasionally mild mesomelic shortening of forearms/legs

C. Endocrine/Metabolic

Condition	Notes
Hypothyroidism	May cause generalized short stature with possible mesomelic prominence
‣	May mimic mesomelic shortening due to short metaphyseal segments