Multicentric infantile myofibromatosis with extensive visceral involvement in a newborn:
Case Report:
With a frequency of approximately 1:150,000, infantile myofibromatosis (IM) is the most common fibrous tumour in newborns. It is characterized by nodules in the skin, muscles, bones, and occasionally in visceral organs. Three clinical subtypes are recognized: disseminated with visceral involvement (DFIM), multicentric without visceral involvement (MFIM), and solitary (SFIM). While SFIM and MFIM are generally associated with good prognoses, DFIM carries a high mortality rate of up to 73%. Although lesions may undergo spontaneous regression, they can also enlarge or recur, necessitating careful and individualized follow-up.
A full-term male neonate presented with multiple firm nodules involving bone, muscle, and soft tissue, along with hepatic and right atrial lesions. Early findings included hyporeactivity, nystagmus, and metabolic abnormalities.
Genomic DNA (gDNA) was extracted from the proband and parents’ peripheral blood (PB) samples for molecular analysis using next-generation sequencing (NGS). Trio-based clinical exome sequencing (CES) was performed with the TruSight One Expanded Sequencing Panel Kit (Illumina, San Diego, CA, USA). Library preparation followed the Nextera Flex for Enrichment protocol (Illumina), and sequencing was performed on the NextSeq 550Dx platform (Illumina). Sequencing data were processed using the NextSeq Control Software v4.2.0 and Local Run Manager v4.0.0 (Illumina). Variant calling and downstream interpretation were conducted using the Geneyx Analysis software v5.15 (Geneyx Genomex Ltd., Tel Aviv, Israel), which identified a paternally inherited PDGFRB intronic variant (c.2905-8G>A).
Given the patient’s low weight and the potential for spontaneous regression, no treatment was initiated. Over the first year of life, he demonstrated normal growth, satisfactory neurodevelopment, and regression of all lesions, with only a stable right atrial mass persisting.
In summary, IM is a rare fibrous neoplasm of infancy that may present sporadically or in familial forms associated with autosomal dominant PDGFRB germline variants, leading to constitutive PDGFRB kinase activation. While localized or multifocal IM without visceral involvement generally has a favourable prognosis with frequent spontaneous regression, disseminated disease affecting visceral organs carries a higher mortality risk. Management often follows a conservative “watch and wait” approach, reserving surgery or chemotherapy for progressive or symptomatic cases. Targeted therapies, such as tyrosine kinase inhibitors (imatinib, sunitinib), show promise in PDGFRB-mutated cases but require careful consideration due to potential long-term effects in infants.
