Syndromes: skeletal & sex Flashcards
What kind of shortening is rhizomelic
Proximal
Spondyloepiphyseal dysplasia, early arthritis, retinal detachment, myopia, cataract, hearing loss, Robin sequence
Stickler syndrome: AD, COL2, COL9, COL11 (abnormal structural collagen)
Knee/hip pain in childhood, need large joint replacement in 30s. Short for family, ragged growth plates on XR.
Multiple epiphyseal dysplasia: AD, COL9, COMP, MATN3 (abnormal structural collagen)
Limb shortening, hitchhiker’s thumb, boxer/cauliflower ears, spinal deformity, early OA, joint contractures
Diastrophic dysplasia: AR, SLC26A2 (IEM of cartilage/sulfate metabolism)
Short fingers, nasomaxillary hypoplasia, stippled epiphyses; mild/minimal
Chondrodysplasia punctata: XL, ARSE (IEM of cartilage metabolism)
Rhizomelic short stature, macrocephaly, midface hypoplasia, frontal bossing, trident hands, genu varum (bow legs), joint hyperextensibility
Achondroplasia: AD GOF of FGFR3, limits cartilage formation/ossification
Complications of achondroplasia in infancy
Hydrocephalus, hypotonia, motor delay, poor drainage of Eustachian tubes, OSA from large adenoid/tonsils & midface hypoplasia + central apnea from foramen magnum narrowing –> 7.5% mortality of apnea
Complications of achondroplasia in childhood/adulthood
Craniocervical junction compression, obesity, back pain (exaggerated lumbar lordosis), spinal stenosis, dental crowding, cardiovascular disease (interestingly no T2DM or arthritis).
Cloverleaf skull, micromelia, short limbs, usually fatal from lung underdevelopment
Thanatophoric dysplasia: AD GOF in FGFR3 (p.Lys650Glu)
Bowed long bones, narrow iliac wings, Robin sequence, pulmonary hypoplasia, 2/3 of male w/ambiguous genitalia
Campomelic dysplasia: AD, SOX9
Variant for achondroplasia vs hypochondroplasia
m.1138G>A, p.Gly380Arg // m.1620C>A or G, p.Asn540Lys
Cataracts, coronal defects of vertebrae, rhizomelia, chondrodysplasia punctata
Rhizomelic chondrodysplasia punctata types 1-3: AR PEXY7, GNPAT, AGPS (peroxisomal)
Rhizomelia, coronal clefts of vertebral bodies, cataracts, male lethal
Chondrodysplasia punctata type 2 aka Conradi-Hunerman syndrome: XD, CDPX2 (peroxisomal/cholesterol synthesis)
Short forearm w/Madelung deformity (curved radius w/step-off at wrist), limited mobility, tibiofibular shortening, short stature. Usually female > male but only short stature w/Turner syndrome…
Leri Weill dysostosis: haploinsufficiency for SHOX or SHOXY, usually with X-chromosome deletion
Aplasia/severe hypoplasia of ulna and fibula, thickened/curved radius and tibia, hypoplasia of mandible
Langer Mesomelic Dysplasia: total KO of SHOX or SHOXY. Very rare.
Absent ossification of lateral parts of clavicles, wide fontanelles and sagittal suture, low bone density.
Cleidocranial dysplasia: Runx2/CBFA1 (osteoblast)
Benign cartilage-capped tumors (osteochondromas); stop forming once growth plate closed, malignant transformation ~1%/year
Hereditary multiple exostoses: AD, EXT1 or EXT2
Osteochondromas + enchondromas
Metachrondromatosis: AD, PTPN11
Fibrous dysplasia of bone (one or many bones), bone pain, pathologic fracture
Somatic mutations in GNAS1
Cafe-au-lait spots w/jagged coastal borders, hyperfunctional endocrine disorders (precocious puberty, hyperthyroidism, excess GH, Cushing syndrome), fibrous dysplasia of bone
McCune-Albright Syndrome: somatic mutations in GNAS1
Multiple fractures, blue sclerae
Osteogenesis imperfecta: AD COL1A1 and 1A2, many AR forms
Osteosclerosis of whole skeleton within months, macrocephaly, frontal bossing, craniosynostosis, hypodontia/malformed teeth +/- hydrocephalus, CN compression (blind/deaf).
Neuronopathic form with seizures, DD, degeneration of retinal/CNS.
Osteopetrosis, caused by defects in mechanisms for osteoclast acidification and digestion of bone.
Infantile malignant: AR TCIRG1, CLCN7 (Cl channel), OSTM1 (neuropathic form)
Short limbs, short stature, obtuse mandibular angle w/convex nasal ridge, osteosclerosis w/bone fragility, delayed closure of cranial sutures, clavicular dysplasia
Pycnodysostosis: AR, CTSK (cathepepsin K)
Later osteopetrosis presentations genes
Intermediate: CLCN7, PLECKHM1, TNFS11 (RANKL)
Late-onset: CLCN7, LRP5
With RTA: AR CA2 (carbonic anhydrase)
Tx of osteopetrosis
Bone marrow transplant to replace osteoclasts (not for neuronopathic form, often OSTM1)
Sertoli vs Leydig cells
Sertoli: spermatogenesis, secrete Mullerian inhibiting factor locally
Leydig: hCG receptors, secrete testosterone locally for Wolffian ducts, external genitalia
Needed for testicular development
SRY
Needed for male external genitalia development
5a reductase changing testosterone -> circulating DHT until puberty