summary Metaphyseal Chondrodysplasia is a heterogeneous group of congenital disorders caused by variety of mutations leading to metaphyseal changes of the tubular bones with normal epiphyses. Patients present with short-limb dwarfism characterized by genu varum, coxa vara, and spinal abnormalities. Diagnosis is made based on family history associated with typical radiographic and clinical features. No commercially available diagnostic test exists due to the variety of genetic mutations. Treatment involves a multidisciplinary approach to improve and maintain function. Surgical spinal fusion is indicated in patients with atlantoaxial instability. Epidemiology Incidence skeletal dysplasias occur at a rate of 2 to 3 newborns per 10,000 births Etiology Pathophysiology metaphyseal dysplasia involving the proliferative and hypertrophic zone of the physis (epiphysis is normal) Genetics three main subtypes Jansen (rare, most severe form) login to view 2 more bullets Schmid (more common, less severe form) login to view 2 more bullets McKusick login to view 3 more bullets Associated conditions birth defects can be mimicked by teratogenic rickets Schmid type often confused for rickets Classification Table of Metaphyseal Chondrodysplasias Type Genetics Characteristics Comments Jansen's Autosomal dominant Defect in parathyroid hormone related peptide (PTHRP) receptor Mental retardation Short limbed dwarfism Wide eyes Monkey like stance Ostebulbous metaphyseal expansion of long bones seen on xray Schmid's Autosomal dominant Defect in Type X collagen Short limbed dwarfism Excessive lumbar lordosis Severe thigh and leg bowing, genu varum Wrist swelling, elbow contractures Trendelenburg gait Diagnosed when patient older due to coxa vara and genu varum Often confused with Ricketts McKusicks Autosomal recessive Cartilage hair dysplasia (hair had small diameter) Atlantoaxial instability Ankle deformity due to fibular overgrowth Immunologic deficiency and increased risk for malignancy Seen in Amish population and in Finland Presentation Jansen type mental retardation markedly-short limbed dwarfism with: wide eyes monkey-like stance hypercalcemia Schmid type often not diagnosed until older age due to marked coxa vara and genu varum short-limbed dwarf involving: Trendelenburg gait predominate proximal femur involvement increased lumbar lordosis normal laboratory results McKusick type common associated with atlantoaxial instability secondary to odontoid hypoplasia ankle deformity due to fibular overgrowth associated with: login to view 4 more bullets Imaging Radiographs Jansen type AP pelvis, hip, knee, and upper extremity radiographs login to view 1 more bullet Schmid type AP pelvis and hip radiographs login to view 1 more bullet standing lower extremity films login to view 1 more bullet McKusick type cervical AP, lateral, flexion and extension views login to view 1 more bullet ankle AP, oblique and lateral views login to view 1 more bullet Metaphyseal dysplasia involving the proliferative and hypertrophic zone of the physis (epiphysis is normal) Treatment Operative posterior atlantoaxial fusion indications login to view 2 more bullets techniques login to view 1 more bullet valgus intertrochanteric osteotomy indications login to view 3 more bullets techniques login to view 3 more bullets tibial osteotomies or hemiepiphysiodeses indications login to view 2 more bullets limb lengthening through a metaphyseal corticotomy indications login to view 1 more bullet