title: A case of severe osteomalacia secondary to phosphate diabetes in a renal transplant recipient.
abstract: Transient hypophosphatemia is frequently observed during the first months after renal transplantation and is usually asymptomatic. Phosphate diabetes is defined as inadequate tubular phosphorus reabsorption leading to persistent renal phosphorus wasting, which is an important but overlooked cause of osteodystrophy in the post-renal transplantation population. We report the case of a 58-year-old male who presented with severe multiple osteoarticular pains within 3 months after successful first kidney transplantation. Bone disease was attributed initially to mild hyperparathyroidism secondary to vitamin D deficiency. Despite the correction of the hyperparathyroidism, the withdrawal of corticosteroids, and the reduction of immunosuppressive treatment to tacrolimus-based monotherapy, the osteoarticular pains persisted. Skeletal investigations at month 9 post-transplantation demonstrated a significant bone mineral density loss associated with osteomalacia and osteoporosis on the bone biopsy. Laboratory data showed persistent hypophosphatemia, and phosphate diabetes was then diagnosed explaining the post-transplant bone disease. A tacrolimus-induced renal tubular disorder was suspected to contribute to the excessive renal phosphorus wasting. The replacement of tacrolimus by sirolimus, in addition to oral phosphorus and vitamin D supplementations, led to the disappearance of pains, the normalization of urinary and plasma phosphate level, and a significant improvement of bone mineralization.
authors.affiliation: LUNAM Université, Angers, France, josayegh@chu-angers.fr.
authors.forename: Johnny
authors.initials: J
authors.lastname: Sayegh
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Augusto
authors.forename: Daniel
authors.initials: D
authors.lastname: Chappard
authors.forename: Paolo
authors.initials: P
authors.lastname: Insalaco
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Subra
mesh_terms: D050071:Bone Density Conservation Agents / Q000627:therapeutic use; D006801:Humans; D006887:Hydroxycholecalciferols / Q000627:therapeutic use; D017674:Hypophosphatemia / Q000188:drug therapy / Q000209:etiology*; D007166:Immunosuppressive Agents / Q000009:adverse effects; D016030:Kidney Transplantation / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D010018:Osteomalacia / Q000188:drug therapy / Q000209:etiology*; D010758:Phosphorus / Q000627:therapeutic use; D020123:Sirolimus / Q000627:therapeutic use; D016559:Tacrolimus / Q000009:adverse effects
chemical_list: D050071:Bone Density Conservation Agents; D006887:Hydroxycholecalciferols; D007166:Immunosuppressive Agents; D010758:Phosphorus; C008088:alfacalcidol; D020123:Sirolimus; D016559:Tacrolimus