Imaging manifestations of juvenile hyaline fibromatosis: A case report and literature review

Objective: Juvenile hyaline fibromatosis (JHF) is an autosomal recessive condition caused by a mutation in capillary morphogenesis gene 2 (CMG2) on chromosome 4q21. JHF is an extremely rare genetic disorder, and fewer than a hundred cases have been reported worldwide. In this case report, the clinical features, histopathological features and imaging manifestations of a case of JHF are presented. We present imaging manifestations of one case of JHF to deepen the radiologist’s understanding of this condition. The histopathological feature of JHF is hyaline degeneration involving skeletal muscle. Therefore, the lesion has a slightly high density on CT imaging, iso- or hypointense signal on T1WI and hypointense signal on T2WI. The boundary between the lesion and skeletal muscle is unclear. Methods: An 8-year-old male (case 1) was examined in our department with a complaint of multiple masses on the head, neck and back in 2021. The boy was the only child of his parents and was delivered at 40 weeks gestation by caesarean section. His parents were nonconsanguineous. Results : JHF displays multiple slowly or rapidly growing subcutaneous nodules. The imaging manifestations can reflect histopathological components, including nodular connective tissue and amorphous, partially calcified hyaline material.

Loss of cGMP-dependent protein kinase II alters ultrasonic vocalizations in mice, a model for speech impairment in human microdeletion 4q21 syndrome

Chromosome 4q21 microdeletion leads to a human syndrome that exhibits restricted growth, facial dysmorphisms, mental retardation, and absent or delayed speech. One of the key genes in the affected region of the chromosome is PRKG2, which encodes cGMP-dependent protein kinase II (cGKII). Mice lacking cGKII exhibit restricted growth and deficits in learning and memory, as seen in the human syndrome. However, speech/vocalization impairments in these mice have not been determined. Moreover, the molecular pathway underlying speech impairment in humans is not fully understood. Here, we employed cGKII knockout (KO) mice as a model for the human microdeletion syndrome to test whether vocalizations are affected by loss of the PRKG2 gene. Mice emit ultrasonic vocalizations (USVs) to communicate in social situations, stress, and isolation. We thus recorded ultrasonic vocalizations as a model for speech in humans. We isolated postnatal day 5-7 pups from the nest to record and analyze USVs and found significant differences in vocalizations of KO mice relative to wild-type and heterozygous mutant mice. KO mice produced fewer calls that were shorter duration, higher frequency, and lower intensity. Because neuronal activity in the hypothalamus is important for the production of animal USVs following isolation from the nest, we assessed hypothalamic activity in KO pups following isolation. Indeed, we found abnormal hyperactivation of hypothalamic neurons in cGKII KO pups after isolation. Taken together, our studies indicate that cGKII is important for neuronal activation in the hypothalamus, which is required for the production of USVs in neonatal mice. We further suggest cGKII KO mice can be a valuable animal model for human microdeletion 4q21 syndrome.HighlightsChromosome 4q21 microdeletion leads to a human syndrome that exhibits restricted growth, mental retardation, and absent or delayed speech.The cGMP-dependent protein kinase II (cGKII) gene is one of the genes located in the affected region of the chromosome.cGKII knockout mice show restricted growth and deficits in learning and memory.Altered ultrasonic vocalizations and abnormal activation in hypothalamic neurons are found when infant cGKII knockout pups are isolated from the nest.cGKII knockout mice can be a valuable animal model for human microdeletion 4q21 syndrome.

Amelogenesis Imperfecta in a New Animal Model—a Mutation in Chromosome 5 (human 4q21)

Candidate genes for amelogenesis imperfecta (AI) and dentinogenesis imperfecta (DI) are located on 4q21 in humans. We tested our hypothesis that mutations in the portion of mouse chromosome 5 corresponding to human chromosome 4q21 would cause enamel and dentin abnormalities. Male C3H mice were injected with ethylnitrosourea (ENU). Within a dominant ENU mutagenesis screen, a mouse mutant was isolated with an abnormal tooth enamel (ATE) phenotype. The structure and ultrastructure of teeth were studied. The mutation was located on mouse chromosome 5 in an interval of 9 cM between markers D5Mit18 and D5Mit10. Homozygotic mutants showed total enamel aplasia with exposed dentinal tubules, while heterozygotic mutants showed a significant reduction in enamel width. Dentin of mutant mice showed a reduced content of mature collagen cross-links. We were able to demonstrate that a mutation on chromosome 5 corresponding to human chromosome 4q21 can cause amelogenesis imperfecta and changes in dentin composition.