Osteopathia striata with cranial sclerosis (OSCS) is an X-linked disease caused by truncating mutations in WTX. Females exhibit sclerotic striations on the long bones, cranial sclerosis, and craniofacial dysmorphism. Males with OSCS have significant skeletal sclerosis, do not have striations but do display a more severe phenotype commonly associated with gross structural malformations, patterning defects, and significant pre- and postnatal lethality. The recent description of mutations in WTX underlying OSCS has led to the identification of a milder, survivable phenotype in males. Individuals with this presentation can have, in addition to skeletal sclerosis, Hirschsprung disease, joint contractures, cardiomyopathy, and neuromuscular anomalies. A diagnosis of OSCS should be considered in males with macrocephaly, skeletal sclerosis that is most marked in the cranium and the absence of metaphyseal striations. The observation of striations in males may be indicative of a WTX mutation in a mosaic state supporting the contention that this sign in females is indicative of the differential lyonization of cells in the osteoblastic lineage.

These data indicate that WTX mutations can arise both early and late in Wilms tumour development. WTX mutations may predispose to nephrogenic rest development rather than Wilms tumour per se.

Osteopathia striata congenita with cranial sclerosis (OSCS) is a skeletal dysplasia caused by germline deletions of or truncating point mutations in the X-linked gene WTX (FAM123B, AMER1). Females present with longitudinal striations of sclerotic bone along the long axis of long bones and cranial sclerosis, with a high prevalence of cleft palate and hearing loss. Intellectual disability or neurodevelopmental delay is not observed in females with point mutations in WTX leading to OSCS. One female has been described with a deletion spanning multiple neighbouring genes suggesting that deletion of some neighbouring loci may result in abnormal neurodevelopment. In this cohort of 13 females with OSCS resulting from deletions of WTX, a relationship is observed where deletion of ARHGEF9 and/or MTMR8 in conjunction with WTX results in an additional neurodevelopmental phenotype whereas deletion of ASB12 along with WTX is associated with a good neurodevelopmental prognosis.

Osteopathia striata with cranial sclerosis (OSCS) is caused by truncating mutations or deletions in the X linked gene, WTX, and is characterized by sclerotic striations of the metaphyses and diaphyses of long bones, pelvis, and scapula, along with craniofacial hyperostosis. Females typically manifest with craniofacial dysmorphisms including macrocephaly, hypertelorism, depressed nasal bridge, and hypoplastic maxilla, often have cleft palate, and less often extra skeletal anomalies. Here we report on a sporadic female patient with OSCS born at 33 weeks, with coarse facies, an abnormal head shape, cleft palate, pyloric stenosis, a small VSD, and laryngotracheomalacia sufficiently severe to require tracheostomy placement. Characteristic radiologic findings were apparent on skeletal survey and cranial CT. At age 5, she showed mild delays in neurodevelopmental milestones. A deletion of WTX and the adjacent gene ASB12 was detected via MLPA and there was no skewing of the X-chromosome inactivation pattern (58:42). Neurodevelopmental delays can manifest in females with OSCS and deletions at the WTX locus, but deletion of the ASB12 gene in this case suggests it is unlikely to contribute to the pathogenesis of this complication. Implication of ASB12 in the patient's other unique features such as laryngotracheomalacia and pyloric stenosis is also unlikely. This case illustrates an early presentation of severe OSCS in a female without skewing of the X-chromosome inactivation pattern, emphasizing the variable expressivity of this disorder.

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