At least 9 IMF cases described in the English literature were diagnosed in fetuses based on the findings of fetal spectrogram and/or magnetic resonance imaging. IMF tumors in the viscera or deep tissues may present with serious or life-threatening signs and symptoms of organ and/or deep tissue damage due to these tumors space-filling and pressuring effects.Some individuals with IMF present with a family history of IMF tumors. To date (2021), 20 families have been reported to carry various germline (i.e. inherited) mutations in one of their two PDGFRB genes. All of these mutations were gain of function mutations (i.e. the mutant genes product is overactive) and inherited in an autosomal dominant manner with incomplete penetrance. Among 36 identified familial carriers of these mutant genes, 4 had no history of IMF, 3 had developed a solitary IMF, 29 had developed multiple tumors (no viscera involvement) or multiple tumors (with viscera involvement) IMF, and 2 had died. Most of these individuals were diagnosed with IMF in their infancy or early childhood. Subsequent studies have found that up to 70% of individuals with IMF and no family history of the disease also carry mutations in one of their two PDGFRB genes in the cells of their tumor tissues. These mutations are somatic mutations (i.e. non-inherited mutations developing only after conception) that are identical or similar to those seen in familial cases. The familial and non-familial mutated PDGFRB genes produce highly overactive platelet-derived growth factor receptor beta (i.e.
Infantile myofibromatosis (IMF) is a rare tumor found in 1 in 150,000 to 1 in 400,000 live births. It is nonetheless the most common tumor derived from fibrous connective tissue that occurs primarily in infants and young children. IMF tumors are benign in the sense that they do not metastasize to distant tissues although when occurring in the viscera, i.e. internal organs, carry guarded to poor prognoses and can be life-threatening, particularly in newborns and young infants.IMF tumors occur in three clinical patterns: 1) solitary IMF tumors (also called myofibromas) which often regress spontaneously and rarely cause serious issues; 2) multiple tumors (no viscera involvement) which consists of numerous (i.e. dozens to >100) IMF lesions most of which are located in the skin, subcutaneous tissues, and non-visceral but not visceral organs, may regress spontaneously, and rarely cause serious issues; and 3) multiple tumors (with viscera involvement) (also called generalized myofibromatosis) which rarely regress spontaneously and consist of numerous IMF lesions in non-visceral tissues plus one or more visceral tumors that may be life-threatening.A minority of infantile myofibromatosis tumors present in individuals with a strong family history of the disease. These familial cases are associated with mutations in either the PDGFRB or NOTCH3 gene. However, most IMF cases have no family history of the disease but nonetheless have PDGFRB gene mutations in their tumor cells; these mutations are similar to those occurring in the familial PDGFRB gene mutations. Regardless of these genetic variations, all IMF tumors consist of bland-appearing, benign (i.e. non-malignant) myofibroblasts, i.e.