Progressive diaphyseal dysplasia (MIM 131300), also known as Camurati–Engelmann disease (CED), is a rare autosomal dominant craniotubular dysplasia caused by mutations in the transforming growth factor beta1 (TGF-β1) gene. Radiographs of the long bones of a 9-year-old boy presenting with waddling gait, muscular weakness, underweight, and severe skeletal pain showed symmetric diaphyseal cortical thickening pathognomonic for CED. The diagnosis was verified by detecting a mutation in exon 4 of the TGF-β1 gene. Full body bone mineral densitometry studies performed before treatment with prednisolone were indicative for osteoporosis (Z-scores for the lumbar spine and femoral neck −2.3 and −3.2, respectively). A transiliac bone biopsy showed markedly reduced trabecular bone volume. Oral prednisolone was initiated, and subsequently, pamidronate infusions were commenced in an attempt to prevent progression of osteoporosis. To our knowledge, this is the first time bone biopsy and bone mineral densitometry studies have been performed and bisphosphonate treatment evaluated in a child with CED.