Osteogenesis imperfecta (OI) is a heritable connective tissue disorder that causes bone fragility due to pathogenic variants in genes responsible for the synthesis of type I collagen. Efforts to classify the high clinical variability in OI led to the Sillence classification. However, this classification only partially takes into account extraskeletal manifestations and the high genetic variability. Little is known about the relation between genetic variants and phenotype as of yet. The aim of the study was to create a clinically relevant genetic stratification of a cohort of 675 Dutch OI patients based on their pathogenic variant types and to provide an overview of their respective medical care demands. The clinical records of 675 OI patients were extracted from the Amsterdam UMC Genome Database and matched with the records from Statistics Netherlands (CBS). The patients were categorized based on their harbored pathogenic variant. The information on hospital admissions, outpatient clinic visits, medication, and diagnosis-treatment combinations (DTCs) was compared between the variant groups. OI patients in the Netherlands appear to have a higher number of DTCs, outpatient clinic visits, and hospital admissions when compared to the general Dutch population. Furthermore, medication usage seems higher in the OI cohort in comparison to the general population. The patients with a COL1A1 or COL1A2 dominant negative missense non-glycine substitution appear to have a lower health care need compared to the other groups, and even lower than patients with COL1A1 or COL1A2 haploinsufficiency. It would be useful to include the variant type in addition to the Sillence classification when categorizing a patient\'s phenotype.

Familial exudative vitreoretinopathy (FEVR) is a hereditary retinal vascular disorder. Among the various clinical phenotypes of this disease, retinal folds are the primary and typical feature of FEVR. However, little is known about the clinical characteristics, genetic spectrum, or potential phenotype-genotype correlation of retinal folds. Herein, we describe and analyze the clinical and genetic characteristics of retinal folds in FEVR. Eighty-nine patients with unilateral or bilateral retinal folds were included in this study. Clinical examinations showed that the retinal folds were bilateral in 37 patients (41.6%). Various retinal abnormalities were noted in the fellow eyes in the remaining 52 patients with unilateral folds. Most of the folds were located temporally (98.4%, 124/126), and were complete (97.6%, 123/126). 67.5% (60/89) probands were genetic confirmed FEVR. 25 novel pathogenic mutations (7 in FZD4, 7 in LRP5, 1 in NDP, 4 in TSPAN12, and 6 in KIF11) were identified in 25 families. Overall, 87.5% (14/16) and 73.7%(14/19) patients with LRP5 and FZD4 mutations were with unilateral folds, respectively.Nevertheless, only 25% (2/8), 36.4%(4/11) and 16.7%(1/6) patients with NDP, TSPAN12, and KIF11 mutations were with unilateral folds. Moreover, 85.7%(12/14),100% (6/6) and 100%(8/8) of the patients with mutated TSPAN12, KIF11, and NDP genes presented with symmetry in disease staging, while 55% and 64.7% of patients with FZD4 and LRP5 mutation displayed symmetry in staging. In conclusion, the majority of retinal folds extended completely and radially in the temporal peripheral retina. Patients with causative mutations in NDP, TSPAN12, or KIF11 were more likely to have bilaterally symmetrical severe retinopathy. In contrast, patients with LRP5 and FZD4 mutations displayed a relatively milder but broader spectrum of phenotypes and a higher frequency of asymmetry.

Nail-patella syndrome (NPS) is an autosomal dominant disease that typically involves the nails, knees, elbows and the presence of iliac horns. In addition, some patients develop glomerulopathy or adult-onset glaucoma. NPS is caused by loss-of-function mutations in the LMX1B gene. In this study, phenotype-genotype correlation was analyzed in 9 unrelated Korean children with NPS and their affected family members. The probands included 5 boy and 4 girls who were confirmed to have NPS, as well as 6 of their affected parents. All of the patients (100%) had dysplastic nails, while 13 patients (86.7%) had patellar anomalies, 8 (53.3%) had iliac horns, 6 (40.0%) had elbow contracture, and 4 (26.7%) had nephropathy including one patient who developed end-stage renal disease at age 4.2. The genetic study revealed 8 different LMX1B mutations (5 missense mutations, 1 frame-shifting deletion and 2 abnormal splicing mutations), 6 of which were novel. Genotype-phenotype correlation was not identified, but inter- and intrafamilial phenotypic variability was observed. Overall, these findings are similar to the results of previously conducted studies, and the mechanism underlying the phenotypic variations and predisposing factors of the development and progression of nephropathy in NPS patients are still unknown.