Heterozygous TRPV4 mutations cause a group of skeletal dysplasias characterized by short stature, short trunk, and skeletal deformities. The aim of this study is to compare the natural history of clinical and radiologic features of patients with different TRPV4-related skeletal dysplasias. Thirteen patients with a mutation in TRPV4 were included in the study, and 11 were followed for a median of 6.5 years. The clinical phenotype of five patients was compatible with spondylometaphyseal dysplasia Kozlowski type, three each with metatropic dysplasia and brachyolmia type 3, and one each with spondyloepiphyseal dysplasia Maroteaux type and congenital distal spinal muscular atrophy. Short stature and bone pain when running, walking, and climbing stairs occurred in patients with spondylometaphyseal dysplasia Kozlowski type and metatropic dysplasia from the age of 5 years and worsened with increasing age. Kyphosis was more pronounced with increasing age in these two groups of patients, while severe scoliosis occurred in brachyolmia type 3. In the radiographs of patients with spondylometaphyseal dysplasia Kozlowski type and metatropic dysplasia, severe platyspondyly persisted into adulthood or puberty. The patients with spondylometaphyseal dysplasia Kozlowski type exhibited irregular proximal femora leading to destruction of the femoral head towards the end of puberty, whereas metatropic dysplasia showed marked irregularity and widening of the femoral neck. We also observed that metaphyseal dysplasia in long bones other than the proximal femur was so inconspicuous that it could be ignored in patients with spondylometaphyseal dysplasia Kozlowski type. Comparison of radiologic features that change with age in five different TRPV4-related skeletal dysplasias will be of great benefit in the management of this patient group.

TRPV4-related disorders constitute a broad spectrum of clinical phenotypes including several genetic skeletal and neuromuscular disorders, in which clinical variability and somewhat overlapping features are present. These disorders have previously been considered to be clinically distinct phenotypes before their molecular basis was discovered. However, with the identification of TRPV4 variants in the etiology, they are referred as TRPV4-related disorders (TRPV4-pathies), and are now mainly grouped into skeletal dysplasias and neuromuscular disorders. The skeletal dysplasia group includes metatropic dysplasia, parastremmatic dysplasia, spondyloepiphyseal dysplasia Maroteaux type, spondylometaphyseal dysplasia Kozlowski type, autosomal dominant brachyolmia, and familial digital arthropathy-brachydactyly, whereas the neuromuscular group includes congenital distal spinal muscular atrophy (SMA), scapuloperoneal SMA and Charcot-Marie-Tooth neuropathy type 2C with common manifestations of peripheral neuropathy, joint contractures, and respiratory system involvement. Apart from familial digital arthropathy-brachydactyly, skeletal dysplasia associated with TRPV4 pathogenic variants share some clinical features such as short stature with short trunk, spinal and pelvic changes with varying degrees of long bone involvement. Of note, there is considerable phenotypic overlap within and between both groups. Herein, we report on the clinical and molecular spectrum of 11 patients from six different families diagnosed with TRPV4-related disorders. This study yet represents the largest cohort of patients with TRPV4 variants from a single center in Turkey.