@article {38, title = {Cutaneous skeletal hypophosphatemia syndrome (CSHS) is a multilineage somatic mosaic RASopathy.}, journal = {J Am Acad Dermatol}, volume = {75}, year = {2016}, month = {2016 Aug}, pages = {420-7}, abstract = {

BACKGROUND: We recently demonstrated multilineage somatic mosaicism in cutaneous skeletal hypophosphatemia syndrome (CSHS), which features epidermal or melanocytic nevi, elevated fibroblast growth factor (FGF)-23, and hypophosphatemia, finding identical RAS mutations in affected skin and bone.

OBJECTIVE: We sought to: (1) provide an updated overview of CSHS; (2) review its pathobiology; (3)~present a new patient with CSHS; and (4) discuss treatment modalities.

METHODS: We searched PubMed for "nevus AND rickets," and "nevus AND hypophosphatemia," identifying cases of nevi with hypophosphatemic rickets or elevated serum FGF-23. For our additional patient with CSHS, we performed histopathologic and radiographic surveys of skin and skeletal lesions, respectively. Sequencing was performed for HRAS, KRAS, and NRAS to determine causative mutations.

RESULTS: Our new case harbored somatic activating HRAS p.G13~R mutation in affected tissue, consistent with previous findings. Although the mechanism of FGF-23 dysregulation is unknown in CSHS, interaction between FGF and MAPK pathways may provide insight into pathobiology. Anti-FGF-23 antibody KRN-23 may be useful in managing CSHS.

LIMITATIONS: Multilineage RAS mutation in CSHS was recently identified; further studies on mechanism are unavailable.

CONCLUSION: Patients with nevi in association with skeletal disease should be evaluated for serum phosphate and FGF-23. Further studies investigating the role of RAS in FGF-23 regulation are needed.

}, keywords = {Antibodies, Monoclonal, Antibodies, Monoclonal, Humanized, Fibroblast Growth Factor-23, Fibroblast Growth Factors, Genes, ras, Humans, Mosaicism, Nevus, Pigmented, Osteomalacia, Rickets, Hypophosphatemic, Skin Neoplasms, Syndrome}, issn = {1097-6787}, doi = {10.1016/j.jaad.2015.11.012}, author = {Lim, Young H and Ovejero, Diana and Derrick, Kristina M and Collins, Michael T and Choate, Keith A} } @article {289, title = {Multilineage somatic activating mutations in HRAS and NRAS cause mosaic cutaneous and skeletal lesions, elevated FGF23 and hypophosphatemia.}, journal = {Hum Mol Genet}, volume = {23}, year = {2014}, month = {2014 Jan 15}, pages = {397-407}, abstract = {

Pathologically elevated serum levels of fibroblast growth factor-23 (FGF23), a bone-derived hormone that regulates phosphorus homeostasis, result in renal phosphate wasting and lead to rickets or osteomalacia. Rarely, elevated serum FGF23 levels are found in association with mosaic cutaneous disorders that affect large proportions of the skin and appear in patterns corresponding to the migration of ectodermal progenitors. The cause and source of elevated serum FGF23 is unknown. In those conditions, such as epidermal and large congenital melanocytic nevi, skin lesions are variably associated with other abnormalities in the eye, brain and vasculature. The wide distribution of involved tissues and the appearance of multiple segmental skin and bone lesions suggest that these conditions result from early embryonic somatic mutations. We report five such cases with elevated serum FGF23 and bone lesions, four with large epidermal nevi and one with a giant congenital melanocytic nevus. Exome sequencing of blood and affected skin tissue identified somatic activating mutations of HRAS or NRAS in each case without recurrent secondary mutation, and we further found that the same mutation is present in dysplastic bone. Our finding of somatic activating RAS mutation in bone, the endogenous source of FGF23, provides the first evidence that elevated serum FGF23 levels, hypophosphatemia and osteomalacia are associated with pathologic Ras activation and may provide insight in the heretofore limited understanding of the regulation of FGF23.

}, keywords = {Adolescent, Child, Exome, Female, Fibroblast Growth Factors, Gene Expression Regulation, Developmental, GTP Phosphohydrolases, Humans, Hypophosphatemia, Male, Membrane Proteins, Mutation, Nevus, Nevus, Pigmented, Osteomalacia, Proto-Oncogene Proteins p21(ras), Sequence Analysis, DNA, Skin, Skin Neoplasms}, issn = {1460-2083}, doi = {10.1093/hmg/ddt429}, author = {Lim, Young H and Ovejero, Diana and Sugarman, Jeffrey S and Deklotz, Cynthia M C and Maruri, Ann and Eichenfield, Lawrence F and Kelley, Patrick K and J{\"u}ppner, Harald and Gottschalk, Michael and Tifft, Cynthia J and Gafni, Rachel I and Boyce, Alison M and Cowen, Edward W and Bhattacharyya, Nisan and Guthrie, Lori C and Gahl, William A and Golas, Gretchen and Loring, Erin C and Overton, John D and Mane, Shrikant M and Lifton, Richard P and Levy, Moise L and Collins, Michael T and Choate, Keith A} }