[Hyperparathyroidism associated with hypophosphatemic osteomalacia: case report and review of the literature]

Clinical features and treatment of hypophosphatemia and associated complications induced by Phosphaturic mesenchymal tumors: A case series of six patients

Phosphaturic mesenchymal tumor (PMT) is a rare benign mesenchymal tumor characterized by excessive secretion of fibroblast growth factor 23 (FGF23), leading to phosphate loss and systemic osteomalacia. Despite recent progress in PMT research, no consensus on diagnosis and treatment guidelines has been established. This case series describes the clinical and pathological features of six pathologically confirmed PMT patients treated at the Third Affiliated Hospital of Sun Yat-sen University from 2010 to 2024, aiming to provide new insights for the management of this condition. The patients, consisting of three males and three females with an average age of 44 years and follow-up periods of 0.5 to 4.5 years, presented primarily with muscle pain and lower limb weakness. One patient experienced loose teeth, and two had palpable, painless masses. One case developed hyperphosphatemia, tertiary hyperparathyroidism, and renal impairment after prolonged phosphate supplementation. Tumor localization was achieved using 18F-FDG or 68Ga-DOTATATE Positron Emission Tomography-Computed Tomography(PET/CT) and MRI, followed by complete surgical resection. Pathological examination confirmed PMT, and postoperative recovery was marked by significant symptom relief and normalization of serum phosphate levels. Two patients experienced recurrence within three years but showed no further recurrence following repeat surgery by the last follow-up. The diagnosis of PMT is challenging and may take years, potentially leading to complications due to inadequate treatment. Complete tumor resection remains the primary treatment, generally resulting in a favorable prognosis; however, long-term monitoring is essential to detect potential recurrences and initiate timely interventions.

Tumor-induced osteomalacia

Tumor-induced osteomalacia (TIO), also known as oncogenic osteomalacia, is a rare paraneoplastic syndrome characterized by hypophosphatemia resulting from decreased tubular phosphate reabsorption, with a low or inappropriately normal level of active vitamin D. The culprit tumors of TIO could produce fibroblast growth factor 23 which plays a role in regulating renal Pi handling and 25-hydroxyvitamin D 1α-hydroxylase activity. Chronic hypophosphatemia could eventually lead to inadequate bone mineralization, presenting as osteomalacia. The diagnosis should be considered when patients manifest as hypophosphatemia and osteomalacia, or rickets and needs to be differentiated from other disorders of phosphate metabolism, such as the inhereditary diseases like X-linked hypophosphataemic rickets, autosomal dominant hypophosphataemic rickets, autosomal recessive hypophosphataemic rickets and acquired diseases like vitamin D deficiency. Localization of responsible tumors could be rather difficult since the vast majority are very small and could be everywhere in the body. A combination of thorough physical examination, laboratory tests and imaging techniques should be applied and sometimes a venous sampling may come into handy. The technology of somatostatin-receptor functional scintigraphy markedly facilitates the localization of TIO tumor. Patients undergoing complete removal of the causative neoplasm generally have favorable prognoses while a few have been reported to suffer from recurrence and metastasis. For those undetectable or unresectable cases, phosphate supplements and active vitamin D should be administrated and curative intended radiotherapy or ablation is optional.

Adult-onset hypophosphatemic osteomalacia associated with Sjogren syndrome: Clinical case report

RATIONALE

Hypophosphatemic osteomalacia (HO) is a metabolic bone disease, exhibiting different etiologies such as genetic mutation, tumor induction, dysimmunity, or renal disease. Sjogren's syndrome (SS) is a connective tissue disorder commonly involving exocrine glands; however kidney involvement is also encountered, leading to abnormal phosphorus metabolism, even HO.

PATIENT CONCERNS

A 47-year-old female patient presented progressively worsening pain in the chest wall, back and bilateral lower extremities as well as muscle weakness was referred to our department.

DIAGNOSES, INTERVENTIONS AND OUTCOMES

Due to the laboratory test results, radiographic findings and pathologic results, she was diagnosed with adult-onset HO associated with SS. She was then treated with alkalinization, steroids, neutral phosphate, calcium supplements together with activated vitamin D. So far, she recovered uneventfully with relieved pain and increased serum phosphorus level.

LESSONS

HO may be secondary to renal tubular acidosis of SS patients, and it might be a diagnostic challenge when the kidney involvement in SS is latent and precede the typical sicca symptoms.

Osteomalácia oncogênica: cintilografia com sestamibi-99mTc na localização do tumor

A osteomalácia oncogênica hipofosfatêmica (OOH) é uma síndrome paraneoplásica induzida por tumor, de tecidos mole ou ósseo. Apresenta-se com dor e fraturas, acompanhada de hipofosfatemia, hiperfosfatúria e concentrações plasmáticas de 1,25(OH)2D3 inapropriadamente normais/diminuídas. Após a remoção do tumor, a completa resolução das anormalidades clínicas e bioquímicas é sua maior característica. Uma mulher de 44 anos de idade é descrita no caso com dificuldade para caminhar por causa de dores nos membros inferiores, fraqueza muscular generalizada e hipofosfatemia com relativa hiperfosfatúria. A cintilografia de corpo total com sestamibi-99mTc mostrou acúmulo do radiofármaco no terço superior de coxa esquerda onde pequeno tumor foi detectado no exame pelo ultra-som. Com a retirada do tumor, um lipoma, os sintomas melhoraram após um mês, com recuperação completa ao redor do quarto mês. Neste caso, a cintilografia de corpo inteiro com sestamibi-99mTc foi decisiva na localização do tumor causador da osteomalácia oncogênica.