Table 3.

Inherited Conditions with Multiple Osteochondromas in the Differential Diagnosis of Hereditary Multiple Osteochondromas

Gene / Genetic MechanismDisorderMOIDistinguishing Features of Differential Diagnosis Disorder
Contiguous deletion syndrome involving ALX4, EXT2, & PHF21A 1Potocki-Shaffer syndrome (proximal 11p deletion syndrome) (OMIM 601224)AD
  • Parietal foramina & ossification defects of the skull (See Enlarged Parietal Foramina.)
  • Craniofacial abnormalities, syndactyly, & ID in some affected persons
Contiguous deletion syndrome involving EXT1, RAD21, & TRPS1 Trichorhinophalangeal syndrome II (Langer-Giedion syndrome) AD
  • ID
  • Characteristic craniofacial & digital anomalies
PTPN11 Metachondromatosis (OMIM 156250)AD
  • Assoc w/both osteochondromas & intraosseous enchondromas
  • Tumors occur predominantly in digits, point toward nearby joint, & do not cause shortening or bowing of long bone, joint deformity, or subluxation.

AD = autosomal dominant; ID = intellectual disability; MOI = mode of inheritance

1.

Deletion events invariably remove ALX4 and the adjacent gene, EXT2. PHF21A, which is variably deleted, is highly likely to account for the intellectual disability and facial dysmorphism.

From: Hereditary Multiple Osteochondromas

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