Infantile myofibromatosis: two families supporting autosomal dominant inheritance

Multiple Bone Lesions in an 8-Month-Old Child Presenting with Pathologic Fracture: A Rare Case of Solely Osseous Multicentric Infantile Myofibromatosis

CASE

An otherwise healthy 8-month-old boy presented with a pathologic fracture of the distal aspect of the radius. Further work-up demonstrated widespread osseous lesions of the axial and the appendicular skeleton with no soft-tissue or visceral involvement.

CONCLUSION

Infantile myofibromatosis has a spectrum of severity that demands a careful and complete work-up. In rare cases such as the present one, it can manifest as multiple osseous lesions. The patient in the present case was managed conservatively, with no morbidity demonstrated at 1 year of follow-up.

A recurrent PDGFRB mutation causes familial infantile myofibromatosis

Infantile myofibromatosis (IM) is the most common benign fibrous tumor of soft tissues affecting young children. By using whole-exome sequencing, RNA sequencing, and targeted sequencing, we investigated germline and tumor DNA in individuals from four distinct families with the familial form of IM and in five simplex IM cases with no previous family history of this disease. We identified a germline mutation c.1681C>T (p.Arg561Cys) in platelet-derived growth factor receptor β (PDGFRB) in all 11 affected individuals with familial IM, although none of the five individuals with nonfamilial IM had mutations in this gene. We further identified a second heterozygous mutation in PDGFRB in two myofibromas from one of the affected familial cases, indicative of a potential second hit in this gene in the tumor. PDGFR-β promotes growth of mesenchymal cells, including blood vessels and smooth muscles, which are affected in IM. Our findings indicate p.Arg561Cys substitution in PDGFR-β as a cause of the dominant form of this disease. They provide a rationale for further investigations of this specific mutation and gene to assess the benefits of targeted therapies against PDGFR-β in aggressive life-threatening familial forms of the disease.

Mutations in PDGFRB cause autosomal-dominant infantile myofibromatosis

Infantile myofibromatosis (IM) is a disorder of mesenchymal proliferation characterized by the development of nonmetastasizing tumors in the skin, muscle, bone, and viscera. Occurrence within families across multiple generations is suggestive of an autosomal-dominant (AD) inheritance pattern, but autosomal-recessive (AR) modes of inheritance have also been proposed. We performed whole-exome sequencing (WES) in members of nine unrelated families clinically diagnosed with AD IM to identify the genetic origin of the disorder. In eight of the families, we identified one of two disease-causing mutations, c.1978C>A (p.Pro660Thr) and c.1681C>T (p.Arg561Cys), in PDGFRB. Intriguingly, one family did not have either of these PDGFRB mutations but all affected individuals had a c.4556T>C (p.Leu1519Pro) mutation in NOTCH3. Our studies suggest that mutations in PDGFRB are a cause of IM and highlight NOTCH3 as a candidate gene. Further studies of the crosstalk between PDGFRB and NOTCH pathways may offer new opportunities to identify mutations in other genes that result in IM and is a necessary first step toward understanding the mechanisms of both tumor growth and regression and its targeted treatment.

Infantile myofibromatosis: report on a family with autosomal dominant inheritance and variable penetrance

Infantile myofibromatosis (IM) is a benign tumor occurring in infants and young children. Familial IM is rare and the inheritance pattern of IM is unclear. We report on a unique family with four individuals having IM of varying degrees of severity with autosomal dominant inheritance pattern and variable penetrance.