Orofaciodigital syndrome II (OFD2), also known as Mohr syndrome, is characterized by cleft lip/palate, lobulated tongue with nodules, dental anomalies including tooth agenesis, maxillary hypoplasia, conductive hearing loss, and poly-, syn-, and brachydactyly. Mesomelic shortening of the limbs has also been observed (Mohr, 1941; Gorlin, 1982; Monroe et al., 2016).

Mucopolysaccharidosis type VI (MPS6) is an autosomal recessive lysosomal storage disorder resulting from a deficiency of arylsulfatase B. Clinical features and severity are variable, but usually include short stature, hepatosplenomegaly, dysostosis multiplex, stiff joints, corneal clouding, cardiac abnormalities, and facial dysmorphism. Intelligence is usually normal (Azevedo et al., 2004).

The autosomal dominant TRPV4 disorders (previously considered to be clinically distinct phenotypes before their molecular basis was discovered) are now grouped into neuromuscular disorders and skeletal dysplasias; however, the overlap within each group is considerable. Affected individuals typically have either neuromuscular or skeletal manifestations alone, and in only rare instances an overlap syndrome has been reported. The three autosomal dominant neuromuscular disorders (mildest to most severe) are: Charcot-Marie-Tooth disease type 2C. Scapuloperoneal spinal muscular atrophy. Congenital distal spinal muscular atrophy. The autosomal dominant neuromuscular disorders are characterized by a congenital-onset, static, or later-onset progressive peripheral neuropathy with variable combinations of laryngeal dysfunction (i.e., vocal fold paresis), respiratory dysfunction, and joint contractures. The six autosomal dominant skeletal dysplasias (mildest to most severe) are: Familial digital arthropathy-brachydactyly. Autosomal dominant brachyolmia. Spondylometaphyseal dysplasia, Kozlowski type. Spondyloepiphyseal dysplasia, Maroteaux type. Parastremmatic dysplasia. Metatropic dysplasia. The skeletal dysplasia is characterized by brachydactyly (in all 6); the five that are more severe have short stature that varies from mild to severe with progressive spinal deformity and involvement of the long bones and pelvis. In the mildest of the autosomal dominant TRPV4 disorders life span is normal; in the most severe it is shortened. Bilateral progressive sensorineural hearing loss (SNHL) can occur with both autosomal dominant neuromuscular disorders and skeletal dysplasias.

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.

Vitamin D-dependent rickets is a disorder of bone development that leads to softening and weakening of the bones (rickets). There are several forms of the condition that are distinguished primarily by their genetic causes: type 1A (VDDR1A), type 1B (VDDR1B), and type 2A (VDDR2A). There is also evidence of a very rare form of the condition, called type 2B (VDDR2B), although not much is known about this form.\n\nThe signs and symptoms of vitamin D-dependent rickets begin within months after birth, and most are the same for all types of the condition. The weak bones often cause bone pain and delayed growth and have a tendency to fracture. When affected children begin to walk, they may develop abnormally curved (bowed) legs because the bones are too weak to bear weight. Impaired bone development also results in widening of the areas near the ends of bones where new bone forms (metaphyses), especially in the knees, wrists, and ribs. Some people with vitamin D-dependent rickets have dental abnormalities such as thin tooth enamel and frequent cavities. Poor muscle tone (hypotonia) and muscle weakness are also common in this condition, and some affected individuals develop seizures.\n\nIn vitamin D-dependent rickets, there is an imbalance of certain substances in the blood. An early sign in all types of the condition is low levels of the mineral calcium (hypocalcemia), which is essential for the normal formation of bones and teeth. Affected individuals also develop high levels of a hormone involved in regulating calcium levels called parathyroid hormone (PTH), which leads to a condition called secondary hyperparathyroidism. Low levels of a mineral called phosphate (hypophosphatemia) also occur in affected individuals. Vitamin D-dependent rickets types 1 and 2 can be grouped by blood levels of a hormone called calcitriol, which is the active form of vitamin D; individuals with VDDR1A and VDDR1B have abnormally low levels of calcitriol and individuals with VDDR2A and VDDR2B have abnormally high levels.\n\nHair loss (alopecia) can occur in VDDR2A, although not everyone with this form of the condition has alopecia. Affected individuals can have sparse or patchy hair or no hair at all on their heads. Some affected individuals are missing body hair as well.

Vitamin D-dependent rickets type 2A (VDDR2A) is caused by a defect in the vitamin D receptor gene. This defect leads to an increase in the circulating ligand, 1,25-dihydroxyvitamin D3. Most patients have total alopecia in addition to rickets. VDDR2B (600785) is a form of vitamin D-dependent rickets with a phenotype similar to VDDR2A but a normal vitamin D receptor, in which end-organ resistance to vitamin D has been shown to be caused by a nuclear ribonucleoprotein that interferes with the vitamin D receptor-DNA interaction. For a general phenotypic description and a discussion of genetic heterogeneity of rickets due to disorders in vitamin D metabolism or action, see vitamin D-dependent rickets type 1A (VDDR1A; 264700).

Pseudoachondroplasia is characterized by normal length at birth and normal facies. Often the presenting feature is a waddling gait, recognized at the onset of walking. Typically, the growth rate falls below the standard growth curve by approximately age two years, leading to a moderately severe form of disproportionate short-limb short stature. Joint pain during childhood, particularly in the large joints of the lower extremities, is common. Degenerative joint disease is progressive; approximately 50% of individuals with pseudoachondroplasia eventually require hip replacement surgery.

Schneckenbecken dysplasia (SHNKND) is a perinatally lethal skeletal dysplasia. The German term 'Schneckenbecken' refers to the distinctive, snail-like appearance of the ilia that results from a medial bone projection from the inner iliac margin. Other hallmarks of the disorder include thoracic hypoplasia, severe flattening of the vertebral bodies, and short, thick long bones (summary by Hiraoka et al., 2007).

Spondylometaphyseal dysplasia, corner fracture type (SMDCF) is a skeletal dysplasia characterized by short stature and a waddling gait in early childhood. Short stature may be present at birth or develop in early infancy. Individuals may present with short limbs and/or short trunk. Radiographic features include enlargement and corner fracture-like lesions of the metaphyses, developmental coxa vara, shortened long bones, scoliosis, and vertebral anomalies. Limited joint mobility and chronic pain are common. Vision impairment and glaucoma have been reported.

The Strudwick type of spondyloepimetaphyseal dysplasia (SEMD) is characterized by disproportionate short stature, pectus carinatum, and scoliosis, as well as dappled metaphyses (summary by Tiller et al., 1995).

The phenotypic spectrum of X-linked hypophosphatemia (XLH) ranges from isolated hypophosphatemia to severe lower-extremity bowing. XLH frequently manifests in the first two years of life when lower-extremity bowing becomes evident with the onset of weight bearing; however, it sometimes is not manifest until adulthood, as previously unevaluated short stature. In adults, enthesopathy (calcification of the tendons, ligaments, and joint capsules) associated with joint pain and impaired mobility may be the initial presenting complaint. Persons with XLH are prone to spontaneous dental abscesses; sensorineural hearing loss has also been reported.

Free sialic acid storage disorders (FSASDs) are a spectrum of neurodegenerative disorders resulting from increased lysosomal storage of free sialic acid. Historically, FSASD was divided into separate allelic disorders: Salla disease, intermediate severe Salla disease, and infantile free sialic acid storage disease (ISSD). The mildest type was Salla disease, characterized by normal appearance and absence of neurologic findings at birth, followed by slowly progressive neurologic deterioration resulting in mild-to-moderate psychomotor delays, spasticity, athetosis, and epileptic seizures. Salla disease was named for a municipality in Finnish Lapland where a specific founder variant is relatively prevalent. However, the term Salla has been used in the literature to refer to less severe FSASD. More severe FSASD is historically referred to as ISSD, and is characterized by severe developmental delay, coarse facial features, hepatosplenomegaly, and cardiomegaly; death usually occurs in early childhood.

Thanatophoric dysplasia (TD) is a short-limb skeletal dysplasia that is usually lethal in the perinatal period. TD is divided into subtypes: TD type I is characterized by micromelia with bowed femurs and, uncommonly, the presence of craniosynostosis of varying severity. TD type II is characterized by micromelia with straight femurs and uniform presence of moderate-to-severe craniosynostosis with cloverleaf skull deformity. Other features common to type I and type II include: short ribs, narrow thorax, relative macrocephaly, distinctive facial features, brachydactyly, hypotonia, and redundant skin folds along the limbs. Most affected infants die of respiratory insufficiency shortly after birth. Rare long-term survivors have been reported.

Sponastrime dysplasia is an autosomal recessive spondyloepimetaphyseal dysplasia (SEMD) named for characteristic clinical and radiographic findings, including spine (spondylar) abnormalities, midface hypoplasia with a depressed nasal bridge, and striation of the metaphyses. Additional features include disproportionate short stature with exaggerated lumbar lordosis, scoliosis, coxa vara, limited elbow extension, small dysplastic epiphyses, childhood cataracts, short dental roots, and hypogammaglobulinemia. Radiographically, the abnormalities of the lumbar vertebral bodies are suggested to be the most specific finding because the characteristic metaphyseal striations may not be apparent at young ages. Striking clinical variability in presentation, severity, and associated features has been observed (summary by Burrage et al., 2019).

Neonatal severe hyperparathyroidism usually manifests in the first 6 months of life with severe hypercalcemia, bone demineralization, and failure to thrive. Early diagnosis is critical because untreated NSHPT can be a devastating neurodevelopmental disorder, which in some cases is lethal without parathyroidectomy. Some infants have milder hyperparathyroidism and a substantially milder clinical presentation and natural history (summary by Egbuna and Brown, 2008).

The cartilage-hair hypoplasia – anauxetic dysplasia (CHH-AD) spectrum disorders are a continuum that includes the following phenotypes: Metaphyseal dysplasia without hypotrichosis (MDWH). Cartilage-hair hypoplasia (CHH). Anauxetic dysplasia (AD). CHH-AD spectrum disorders are characterized by severe disproportionate (short-limb) short stature that is usually recognized in the newborn, and occasionally prenatally because of the short extremities. Other findings include joint hypermobility, fine silky hair, immunodeficiency, anemia, increased risk for malignancy, gastrointestinal dysfunction, and impaired spermatogenesis. The most severe phenotype, AD, has the most pronounced skeletal phenotype, may be associated with atlantoaxial subluxation in the newborn, and may include cognitive deficiency. The clinical manifestations of the CHH-AD spectrum disorders are variable, even within the same family.

The Torrance type of platyspondylic lethal skeletal dysplasia (PLSDT) is an autosomal dominant disorder characterized by varying platyspondyly, short ribs with anterior cupping, hypoplasia of the lower ilia with broad ischial and pubic bones, and shortening of the tubular bones with splayed and cupped metaphyses. Histology of the growth plate typically shows focal hypercellularity with slightly enlarged chondrocytes in the resting cartilage and relatively well-preserved columnar formation and ossification at the chondroosseous junction. Though generally lethal in the perinatal period, longer survival has been reported (summary by Zankl et al., 2005).

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.

Spondylometaphyseal dysplasia with cone-rod dystrophy (SMDCRD) is characterized by postnatal growth deficiency resulting in profound short stature, rhizomelia with bowing of the lower extremities, platyspondyly with anterior vertebral protrusions, progressive metaphyseal irregularity and cupping with shortened tubular bones, and early-onset progressive visual impairment associated with a pigmentary maculopathy and electroretinographic evidence of cone-rod dysfunction (summary by Hoover-Fong et al., 2014). Yamamoto et al. (2014) reviewed 16 reported cases of SMDCRD, noting that all affected individuals presented uniform skeletal findings, with rhizomelia and bowed lower limbs observed in the first year of life, whereas retinal dystrophy had a more variable age of onset. There was severe disproportionate short stature, with a final height of less than 100 cm; scoliosis was usually mild. Visual loss was progressive, with stabilization in adolescence.

Vitamin D hydroxylation-deficient rickets type 1B (VDDR1B) is caused by a defect in vitamin D 25-hydroxylation (Molin et al., 2017). The major function of vitamin D is to maintain calcium and phosphate levels in the normal range to support metabolic functions, neuromuscular transmission, and bone mineralization. Disorders of vitamin D metabolism or action lead to defective bone mineralization and clinical features including intestinal malabsorption of calcium, hypocalcemia, secondary hyperparathyroidism, increased renal clearance of phosphorus, and hypophosphatemia. The combination of hypocalcemia and hypophosphatemia causes impaired mineralization of bone that results in rickets and osteomalacia (summary by Liberman and Marx, 2001). Rickets can occur because of inadequate dietary intake or sun exposure or because of genetic disorders. Vitamin D3 (cholecalciferol) is taken in the diet or synthesized in the skin from 7-dehydrocholesterol by ultraviolet irradiation. For vitamin D to be active, it needs to be converted to its active form, 1,25-dihydroxyvitamin D3. Vitamin D is transported in the blood by the vitamin D binding protein (DBP; 139200) to the liver, where vitamin D 25-hydroxylase (CYP2R1; 608713) is the key enzyme for 25-hydroxylation. Vitamin D 25(OH)D3, the major circulating form of vitamin D, is then transported to the kidney, where 25(OH)D3 is hydroxylated at the position of carbon 1 of the A ring, resulting in the active form of vitamin D, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) (summary by Christakos et al., 2010).

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).

X-linked recessive hypophosphatemic rickets (XLHRR) is a form of X-linked hypercalciuric nephrolithiasis, which comprises a group of disorders characterized by proximal renal tubular reabsorptive failure, hypercalciuria, nephrocalcinosis, and renal insufficiency. These disorders have also been referred to as the 'Dent disease complex' (Scheinman, 1998; Gambaro et al., 2004). For a general discussion of Dent disease, see 300009.

Autosomal dominant multiple epiphyseal dysplasia (MED) presents in early childhood, usually with pain in the hips and/or knees after exercise. Affected children complain of fatigue with long-distance walking. Waddling gait may be present. Adult height is either in the lower range of normal or mildly shortened. The limbs are relatively short in comparison to the trunk. Pain and joint deformity progress, resulting in early-onset osteoarthritis, particularly of the large weight-bearing joints.

A rare genetic primary bone dysplasia disorder with characteristics of disproportionate short stature with mesomelic short limbs, leg bowing, lumbar lordosis, brachydactyly, joint laxity and a waddling gait. Radiographs show platyspondyly with central protrusion of anterior vertebral bodies, kyphotic angulation and very short long bones with dysplastic epiphyses and flared, irregular, cupped metaphyses.

Dent disease, an X-linked disorder of proximal renal tubular dysfunction, is characterized by low molecular weight (LMW) proteinuria, hypercalciuria, and at least one additional finding including nephrocalcinosis, nephrolithiasis, hematuria, hypophosphatemia, chronic kidney disease (CKD), and evidence of X-linked inheritance. Males younger than age ten years may manifest only LMW proteinuria and/or hypercalciuria, which are usually asymptomatic. Thirty to 80% of affected males develop end-stage renal disease (ESRD) between ages 30 and 50 years; in some instances ESRD does not develop until the sixth decade of life or later. The disease may also be accompanied by rickets or osteomalacia, growth restriction, and short stature. Disease severity can vary within the same family. Males with Dent disease 2 (caused by pathogenic variants in OCRL) may also have mild intellectual disability, cataracts, and/or elevated muscle enzymes. Due to random X-chromosome inactivation, some female carriers may manifest hypercalciuria and, rarely, renal calculi and moderate LMW proteinuria. Females rarely develop CKD.

Hereditary hypophosphatemic rickets with hypercalciuria (HHRH) is a rare autosomal recessive disorder characterized by the presence of hypophosphatemia secondary to renal phosphate wasting, radiographic and/or histologic evidence of rickets, limb deformities, muscle weakness, and bone pain. HHRH is distinct from other forms of hypophosphatemic rickets in that affected individuals present with hypercalciuria due to increased serum 1,25-dihydroxyvitamin D levels and increased intestinal calcium absorption (summary by Bergwitz et al., 2006).

Metaphyseal dysostosis-intellectual disability-conductive deafness syndrome is characterised by metaphyseal dysplasia, short-limb dwarfism, mild intellectual deficit and conductive hearing loss, associated with repeated episodes of otitis media in childhood. It has been described in three brothers born to consanguineous Sicilian parents. Variable manifestations included hyperopia and strabismus. The mode of inheritance is autosomal recessive.

Sedaghatian-type spondylometaphyseal dysplasia (SMDS) is a rare lethal disorder characterized by severe metaphyseal chondrodysplasia with mild limb shortening, platyspondyly, delayed epiphyseal ossification, irregular iliac crests, and pulmonary hemorrhage. Affected infants present with severe hypotonia and cardiorespiratory problems; most die within days of birth due to respiratory failure. Cardiac abnormalities include conduction defects, complete heart block, and structural anomalies. Half of infants with SMDS are reported to have central nervous system malformations consistent with abnormal neuronal migration, including agenesis of the corpus callosum, pronounced frontotemporal pachygyria, simplified gyral pattern, partial lissencephaly, and severe cerebellar hypoplasia (summary by Smith et al., 2014).

Spondyloepimetaphyseal dysplasia with joint laxity type 2 (SEMDJL2) is characterized by short stature, distinctive midface retrusion, progressive knee malalignment (genu valgum and/or varum), generalized ligamentous laxity, and mild spinal deformity. Intellectual development is not impaired. Radiographic characteristics include significantly retarded epiphyseal ossification that evolves into epiphyseal dysplasia and precocious osteoarthritis, metaphyseal irregularities and vertical striations, constricted femoral neck, slender metacarpals and metatarsals, and mild thoracolumbar kyphosis or scoliosis with normal or mild platyspondyly (summary by Min et al., 2011). For a discussion of genetic heterogeneity of SEMD with joint laxity, see SEMDJL1 (271640).

Spondyloepiphyseal dysplasia of the Genevieve type (SEMDG) is characterized by infantile-onset severe developmental delay and skeletal dysplasia, including short stature, premature carpal ossification, platyspondyly, longitudinal metaphyseal striations, and small epiphyses (summary by van Karnebeek et al., 2016).

Shohat-type spondyloepimetaphyseal dysplasia (SEMDSH) is a chondrodysplasia characterized by vertebral, epiphyseal, and metaphyseal abnormalities, including scoliosis with vertebral compression fractures, flattened vertebral bodies, and hypomineralization of long bones. Affected individuals may exhibit a small trunk, short neck, small limbs, joint laxity, bowlegs, and/or abdominal distention with hepatosplenomegaly (summary by Egunsola et al., 2017).

Thanatophoric dysplasia (TD) is a short-limb skeletal dysplasia that is usually lethal in the perinatal period. TD is divided into subtypes: TD type I is characterized by micromelia with bowed femurs and, uncommonly, the presence of craniosynostosis of varying severity. TD type II is characterized by micromelia with straight femurs and uniform presence of moderate-to-severe craniosynostosis with cloverleaf skull deformity. Other features common to type I and type II include: short ribs, narrow thorax, relative macrocephaly, distinctive facial features, brachydactyly, hypotonia, and redundant skin folds along the limbs. Most affected infants die of respiratory insufficiency shortly after birth. Rare long-term survivors have been reported.

Vitamin D-dependent rickets type 2B with normal vitamin D receptor (VDDR2B) is an unusual form of rickets due to abnormal expression of a hormone response element-binding protein that interferes with the normal function of the vitamin D receptor. Vitamin D-dependent rickets type 2A (VDDR2A) is caused by mutation in the vitamin D receptor gene (VDR; 601769), and most patients have alopecia in addition to rickets. For a general phenotypic description and a discussion of genetic heterogeneity of rickets due to disorders in vitamin D metabolism or action, see vitamin D-dependent rickets type 1A (VDDR1A; 264700).

Spondylo-megaepiphyseal-metaphyseal dysplasia is a rare autosomal recessive skeletal dysplasia characterized by disproportionate short stature with a short and stiff neck and trunk; relatively long limbs that may show flexion contractures of the distal joints; delayed and impaired ossification of the vertebral bodies and the presence of large epiphyseal ossification centers and wide growth plates in the long tubular bones; and numerous pseudoepiphyses of the short tubular bones in hands and feet (summary by Hellemans et al., 2009).

Any metaphyseal anadysplasia in which the cause of the disease is a mutation in the MMP9 gene.

Smith-McCort dysplasia is a rare autosomal recessive osteochondrodysplasia characterized by short trunk dwarfism with a barrel-shaped chest, rhizomelic limb shortening, and specific radiologic features including marked platyspondyly with double-humped end-plates, kyphoscoliosis, metaphyseal irregularities, laterally displaced capital femoral epiphyses, and small pelvis with a lace-like appearance of iliac crests. These clinical and radiologic features are also common to Dyggve-Melchior-Clausen syndrome (DMC; 223800), which is distinguished from SMC by the additional feature of mental retardation (summary by Dupuis et al., 2013). For a discussion of genetic heterogeneity of Smith-McCort dysplasia, see SMC1 (607326).

Any Smith-McCort dysplasia in which the cause of the disease is a mutation in the DYM gene.

CAGSSS, which comprises cataracts, growth hormone deficiency, sensory neuropathy, sensorineural hearing loss, and skeletal dysplasia, is an autosomal recessive multisystemic disorder with a highly variable phenotypic spectrum. Not all of these features are always present, and almost all the features may present at different times and/or become more apparent with age. The skeletal features are consistent with spondyloepimetaphyseal dysplasia (SEMD) (summary by Vona et al., 2018). One family had a distinctive presentation with infantile-onset intractable seizures and cortical abnormalities reminiscent of Leigh syndrome (see 256000). The correlation between genotype and phenotype remains unclear, but since the IARS2 gene is involved in mitochondrial function, heterogeneous manifestations can be expected (Takezawa et al., 2018).

Rhizomelic chondrodysplasia punctata (RCDP) is a peroxisomal disorder characterized by disproportionately short stature primarily affecting the proximal parts of the extremities, a typical facial appearance including a broad nasal bridge, epicanthus, high-arched palate, dysplastic external ears, and micrognathia, congenital contractures, characteristic ocular involvement, dwarfism, and severe mental retardation with spasticity. Biochemically, plasmalogen synthesis and phytanic acid alpha-oxidation are defective. Most patients die in the first decade of life (summary by Wanders and Waterham, 2005). For a discussion of genetic heterogeneity of rhizomelic chondrodysplasia punctata, see 215100.

Short-rib thoracic dysplasia (SRTD) with or without polydactyly refers to a group of autosomal recessive skeletal ciliopathies that are characterized by a constricted thoracic cage, short ribs, shortened tubular bones, and a 'trident' appearance of the acetabular roof. SRTD encompasses Ellis-van Creveld syndrome (EVC) and the disorders previously designated as Jeune syndrome or asphyxiating thoracic dystrophy (ATD), short rib-polydactyly syndrome (SRPS), and Mainzer-Saldino syndrome (MZSDS). Polydactyly is variably present, and there is phenotypic overlap in the various forms of SRTDs, which differ by visceral malformation and metaphyseal appearance. Nonskeletal involvement can include cleft lip/palate as well as anomalies of major organs such as the brain, eye, heart, kidneys, liver, pancreas, intestines, and genitalia. Some forms of SRTD are lethal in the neonatal period due to respiratory insufficiency secondary to a severely restricted thoracic cage, whereas others are compatible with life (summary by Huber and Cormier-Daire, 2012 and Schmidts et al., 2013). There is phenotypic overlap with the cranioectodermal dysplasias (Sensenbrenner syndrome; see CED1, 218330). Genetic Heterogeneity of Asphyxiating Thoracic Dysplasia SRTD1 has been mapped to chromosome 15q13. See also SRTD2 (611263), caused by mutation in the IFT80 gene (611177); SRTD3 (613091), caused by mutation in the DYNC2H1 gene (603297); SRTD4 (613819), caused by mutation in the TTC21B gene (612014); SRTD5 (614376), caused by mutation in the WDR19 gene (608151); SRTD6 (263520), caused by mutation in the NEK1 gene (604588); SRTD7 (614091), caused by mutation in the WDR35 gene (613602); SRTD8 (615503), caused by mutation in the WDR60 gene (615462); SRTD9 (266920), caused by mutation in the IFT140 gene (614620); SRTD10 (615630), caused by mutation in the IFT172 gene (607386); SRTD11 (615633), caused by mutation in the WDR34 gene (613363); SRTD13 (616300), caused by mutation in the CEP120 gene (613446); SRTD14 (616546), caused by mutation in the KIAA0586 gene (610178); SRTD15 (617088), caused by mutation in the DYNC2LI1 gene (617083); SRTD16 (617102), caused by mutation in the IFT52 gene (617094); SRTD17 (617405), caused by mutation in the TCTEX1D2 gene (617353); SRTD18 (617866), caused by mutation in the IFT43 gene (614068); SRTD19 (617895), caused by mutation in the IFT81 gene (605489); SRTD20 (617925), caused by mutation in the INTU gene (610621); and SRTD21 (619479), caused by mutation in the KIAA0753 gene (617112). See also SRTD12 (Beemer-Langer syndrome; 269860).

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.

Ververi-Brady syndrome (VEBRAS) is characterized by mild developmental delay, mildly impaired intellectual development and speech delay, and mild dysmorphic facial features. Affected individuals can usually attend mainstream schools with support, and may also show autistic features (summary by Ververi et al., 2018).

Rhizomelic skeletal dysplasia with or without Pelger-Huet anomaly (SKPHA) is an autosomal recessive disorder characterized by rhizomelic skeletal dysplasia of variable severity with or without abnormal nuclear shape and chromatin organization in blood granulocytes (Hoffmann et al., 2002; Borovik et al., 2013; Collins et al., 2020). Initial skeletal features may improve with age (Sobreira et al., 2014).

Krakow-type spondyloepimetaphyseal dysplasia is characterized by severe skeletal dysplasia, severe immunodeficiency, and developmental delay (Csukasi et al., 2018).

Spondyloepimetaphyseal dysplasia with joint laxity-3 (SEMDJL3) is characterized by multiple joint dislocations at birth, severe joint laxity, scoliosis, gracile metacarpals and metatarsals, delayed bone age, and poorly ossified carpal and tarsal bones (Girisha et al., 2016). For a discussion of genetic heterogeneity of SEMD with joint laxity, see SEMDJL1 (271640).

Acromesomelic dysplasia-4 (AMD4) is characterized by disproportionate short stature due to mesomelic shortening of the limbs. Radiographic hallmarks include mild to moderate platyspondyly, moderate brachydactyly, iliac flaring, and metaphyseal alterations of the long bones that progressively increase with age (Diaz-Gonzalez et al., 2022). For a discussion of genetic heterogeneity of acromesomelic dysplasia, see AMD1 (602875).