Twins with Juvenile Hyaline Fibromatosis

Background: Juvenile hyaline fibromatosis (JAF) is a rare autosomal-recessive disease in which patients progressively develop cutaneous tumoral fibroblastic proliferations, and joint contractures with bone involvement. JAF is caused by aberrant synthesis of glycosaminoglycans by fibroblasts due to a mutation of the capillary morphogenesis factor-2 gene (CMG2). Limited treatment options are available. Method: We report monozygotic twins who presented with multiple, recurrent, painless cutaneous nodules. Result: The presence of twins with JAF is extremely rare. A lesion on the head of one boy had ruptured, and pathological analysis indicated benign spindle cells in a periodic acid-Schiff (PAS)-positive hyaline background. One of twins had much more severe clinical presentation than the other, including more frequent diarrhea, larger nodules, more severe joint involvement, and more easily ruptured masses. Conclusion: Monozygotic twins who present with JAF may have different severity of symptoms despite the presence of identical mutations in CMG2.