Differential Diagnosis for Low Calcium, Low Vitamin D, and Low Alkaline Phosphatase in a 16 y/o Female with Years of Bone/Joint Pain

• Single Most Likely Diagnosis
  • Rickets: This condition is characterized by softening of the bones due to a lack of vitamin D, calcium, or phosphate. The patient's symptoms of low calcium, low vitamin D, and low alkaline phosphatase, along with years of bone and joint pain, align closely with rickets, especially given her age and the fact that rickets can present in adolescents if the deficiency persists or begins during this period.
• Other Likely Diagnoses
  • Osteomalacia: Similar to rickets but occurring in adults, osteomalacia is characterized by the softening of bones due to a deficiency of vitamin D and calcium. Although the patient is 16, the prolonged nature of her symptoms could suggest a condition that has been ongoing since childhood, potentially evolving into a form similar to osteomalacia.
  • Hypoparathyroidism: This condition involves the underproduction of parathyroid hormone, which is crucial for regulating calcium levels in the blood. It could explain the low calcium levels but would typically be associated with elevated phosphate levels, which are not mentioned. However, it remains a consideration due to the critical role of parathyroid hormone in calcium homeostasis.
• Do Not Miss Diagnoses
  • Vitamin D-dependent rickets type 1: This is a rare genetic disorder affecting the enzyme responsible for converting vitamin D into its active form. It's crucial to consider genetic causes, especially in cases where nutritional deficiencies have been ruled out or are not fully explanatory.
  • Pseudohypoparathyroidism: A rare genetic disorder characterized by resistance to parathyroid hormone, leading to a variety of biochemical abnormalities, including low calcium levels. It's a "do not miss" diagnosis due to its potential for significant morbidity if left untreated.
• Rare Diagnoses
  • Phosphate diabetes (Vitamin D-resistant rickets): A rare genetic disorder characterized by impaired phosphate reabsorption in the kidneys, leading to rickets or osteomalacia despite normal levels of vitamin D and calcium.
  • Hereditary hypophosphatemic rickets with hypercalciuria: Although this condition typically presents with elevated calcium levels in the urine, its consideration is warranted in cases of resistant rickets or when standard treatments for rickets or osteomalacia fail to improve the patient's condition.