Upper-extremity phocomelia reexamined: a longitudinal dysplasia

Area of Science:

• Orthopedics
• Developmental Biology
• Genetics

Background:

• Phocomelia is traditionally classified as a transverse, intercalated segmental dysplasia of the upper extremity.
• However, many cases present with severe, unclassifiable deformities that do not fit established phocomelia groups.
• These extremities often show abnormalities proximal and distal to the apparent defect, suggesting a different underlying pathology.

Purpose of the Study:

• To investigate whether upper-extremity abnormalities diagnosed as phocomelia represent a proximal continuum of radial or ulnar longitudinal dysplasia.
• To re-evaluate the classification of severe upper-extremity deformities.

Main Methods:

• Retrospective review of medical charts and radiographs of 41 patients (60 extremities) diagnosed with upper-extremity phocomelia.
• Classification of deformities into three groups based on radiographic findings: proximal radial longitudinal dysplasia, proximal ulnar longitudinal dysplasia, and severe combined dysplasia (Types A and B).

Main Results:

• 29 limbs (16 patients) classified as proximal radial longitudinal dysplasia, often associated with thrombocytopenia-absent radius syndrome.
• 20 limbs (17 patients) classified as proximal ulnar longitudinal dysplasia, with common associated musculoskeletal abnormalities like proximal femoral focal deficiency.
• 11 limbs (10 patients) classified as severe combined dysplasia (7 Type A, 4 Type B), with some Type B cases showing contralateral ulnar longitudinal dysplasia and congenital cardiac anomalies.

Conclusions:

• Cases previously diagnosed as upper-extremity phocomelia are proposed to be part of a spectrum of severe longitudinal dysplasia.
• None of the studied extremities exhibited a true intercalary deficiency, supporting the reclassification.
• These findings have significant implications for understanding limb development and genetic factors in congenital abnormalities.