Purpose or Case Report: Rubinstein-Taybi Syndrome (RTS) and infantile myofibromatosis (IM) are both rare genetic disorders. RTS is marked by craniofacial dysmorphism, short stature, and skeletal abnormalities, while IM usually appears as one or more soft tissue nodules, which can affect bones and visceral organs. We present the rare case of a male newborn diagnosed with both RTS and IM. At birth, the patient showed unusual facial features, small size, and polydactyly. The initial skeletal survey showed multiple lucent lesions in the metaphyseal long bones. A follow-up skeletal survey at four months showed growing lucent lesions, though they had developed benign features of a sclerotic rim and a narrow zone of transition. New bone lesions were seen in the flat bones and spine with vertebra plana deformity. Additionally, calcified soft tissue masses were found. Further characterization by MRI suggested marrow infiltration of the lesions. Due to the higher cancer risk in RTS patients, leukemia, lymphoma, or metastatic neuroblastoma were the main concerns, while Langerhans cell histiocytosis was considered less likely due to the metaphyseal pattern. A bone biopsy at two sites confirmed multicentric myofibroma, consistent with IM. Genetic testing found a PDGFRB mutation linked to IM. The patient’s mother tested positive for the same mutation and recalled skin involvement as an infant. The patient tested positive for a de novo CREBBP mutation linked to RTS. These findings suggested autosomal dominant inheritance of IM, while RTS arose sporadically. A whole-body MRI ruled out visceral involvement, a good prognostic factor for IM. The patient received chemotherapy and responded well until it was stopped due to adverse effects. At age 8, he had surgery for a tethered cord, a known complication of RTS. Shortly after, a new lucent lesion, likely a recurrent myofibroma in the right femoral neck, was incidentally found on an abdominal X-ray obtained for pain. The patient is currently under clinical and imaging surveillance. No reported case has yet shown the coexistence of RTS and IM, and there is no known link between the two. This case highlights the importance of considering IM and other rare conditions in the differential diagnosis of multiple lucent bone lesions. A coexisting syndrome can complicate the picture and delay diagnosis. Imaging, biopsy, and genetic testing were key in diagnosing and managing this case.
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