Schmid metaphyseal chondrodysplasia (SMCD) is characterized by progressive short stature that develops by age two years. The clinical and radiographic features are usually not present at birth, but manifest in early childhood with short limbs, genu varum, and waddling gait. Facial features and head size are normal. Radiographs show metaphyseal irregularities of the long bones (e.g., splaying, flaring, cupping); shortening of the tubular bones; widened growth plates; coxa vara; and anterior cupping, sclerosis, and splaying of the ribs. Mild hand involvement often includes shortening of the tubular bones and metaphyseal cupping of the metacarpals and proximal phalanges. Platyspondyly and vertebral end-plate irregularities are less common. Hand and vertebral involvement can resolve with age. Early motor milestones may be delayed due to orthopedic complications. Intelligence is normal. Joint pain in the knees and hips is common and may limit physical activity. Adult height is typically more than 3.5 SD below the mean, although a wide spectrum that overlaps normal height has been reported. There are no extraskeletal manifestations.

A rare, genetic, primary bone dysplasia disease characterized by usually moderate, postnatal short stature, progressive genu vara deformity, a waddling gait, and radiological signs of metaphyseal dysplasia (i.e. irregular, sclerotic and widened metaphyses), in the absence of biochemical abnormalities suggestive of rickets disease. Intermittent knee pain, lordosis, and delayed motor development may also occasionally be associated.

The spondylometaphyseal dysplasias are a relatively common, heterogeneous group of disorders characterized by spinal and metaphyseal changes of variable pattern and severity. The classification of spondylometaphyseal dysplasias of Maroteaux and Spranger (1991) was based on changes of the femoral neck and the shape of vertebral anomalies. In this classification, type A4 referred to a form with severe metaphyseal changes of the femoral neck and ovoid, flattened vertebral bodies with anterior tongue-like deformities.

Spondyloenchondrodysplasia with immune dysregulation (SPENCDI) is an immunoosseous dysplasia combining the typical metaphyseal and vertebral bone lesions of spondyloenchondrodysplasia (SPENCD) with immune dysfunction and neurologic involvement. The skeletal dysplasia is characterized by radiolucent and irregular spondylar and metaphyseal lesions that represent islands of chondroid tissue within bone. The vertebral bodies show dorsally accentuated platyspondyly with disturbance of ossification. Clinical abnormalities such as short stature, rhizomelic micromelia, increased lumbar lordosis, barrel chest, facial anomalies, and clumsy movements may be present (Menger et al., 1989). Central nervous system involvement includes spasticity, mental retardation, and cerebral calcifications, and immune dysregulation ranges from autoimmunity to immunodeficiency. Neurologic and autoimmune manifestations have been observed in different combinations within a single family, suggesting that this disorder may be defined by specific radiographic features but has remarkably pleiotropic manifestations (Renella et al., 2006). Briggs et al. (2016) also noted variability in skeletal, neurologic, and immune phenotypes, which was sometimes marked between members of the same family. Classification of the Enchondromatoses In their classification of the enchondromatoses, Spranger et al. (1978) called Ollier disease and Maffucci syndrome types I and II enchondromatosis, respectively; metachondromatosis (156250), type III; and spondyloenchondrodysplasia (SPENCD), also called spondyloenchondromatosis, type IV; enchondromatosis with irregular vertebral lesions, type V; and generalized enchondromatosis, type VI. Halal and Azouz (1991) added 3 tentative categories to the 6 in the classification of Spranger et al. (1978). Pansuriya et al. (2010) suggested a new classification of enchondromatosis (multiple enchondromas).

Any autosomal recessive primary microcephaly in which the cause of the disease is a mutation in the CENPE gene.

Dyskeratosis congenita and related telomere biology disorders (DC/TBD) are caused by impaired telomere maintenance resulting in short or very short telomeres. The phenotypic spectrum of telomere biology disorders is broad and includes individuals with classic dyskeratosis congenita (DC) as well as those with very short telomeres and an isolated physical finding. Classic DC is characterized by a triad of dysplastic nails, lacy reticular pigmentation of the upper chest and/or neck, and oral leukoplakia, although this may not be present in all individuals. People with DC/TBD are at increased risk for progressive bone marrow failure (BMF), myelodysplastic syndrome or acute myelogenous leukemia, solid tumors (usually squamous cell carcinoma of the head/neck or anogenital cancer), and pulmonary fibrosis. Other findings can include eye abnormalities (epiphora, blepharitis, sparse eyelashes, ectropion, entropion, trichiasis), taurodontism, liver disease, gastrointestinal telangiectasias, and avascular necrosis of the hips or shoulders. Although most persons with DC/TBD have normal psychomotor development and normal neurologic function, significant developmental delay is present in both forms; additional findings include cerebellar hypoplasia (Hoyeraal Hreidarsson syndrome) and bilateral exudative retinopathy and intracranial calcifications (Revesz syndrome and Coats plus syndrome). Onset and progression of manifestations of DC/TBD vary: at the mild end of the spectrum are those who have only minimal physical findings with normal bone marrow function, and at the severe end are those who have the diagnostic triad and early-onset BMF.

Shwachman-Diamond syndrome (SDS) is characterized by: exocrine pancreatic dysfunction with malabsorption, malnutrition, and growth failure; hematologic abnormalities with single- or multilineage cytopenias and susceptibility to myelodysplasia syndrome (MDS) and acute myelogeneous leukemia (AML); and bone abnormalities. In almost all affected children, persistent or intermittent neutropenia is a common presenting finding, often before the diagnosis of SDS is made. Short stature and recurrent infections are common.