Presentation
Known history of cystinosis, Fanconi syndrome, and short stature presenting for follow up imaging.
Patient Data
Bilateral kidneys that are small for age with diffuse increased cortical echogenicity and decreased corticomedullary differentiation consistent with chronic renal disease. No hydronephrosis.
Bone age study done at age 8 showing bone age between 5 years 9 months and 6 years 10 months, less than 2 standard deviations of the chronological age and hence delayed. Mild diffuse osteopenia and cupping of distal radial and ulnar metaphyses is concerning for Rickets.
Case Discussion
This case shows the sequelae of infantile cystinosis, which is a lysosomal storage disease causing accumulation of cystine in multiple organs. The patient was diagnosed with increased levels of leukocyte cysteine as an infant at an outside hospital. As in this patient, cystinosis can lead to impaired proximal tubular reabsorption manifesting as Fanconi syndrome as early as 6 months of age. This patient shows evidence of chronic medical renal disease at age 9. Fanconi syndrome manifests by hypokalemia, hypophosphatemia, and metabolic acidosis. Fanconi syndrome can lead to vitamin D-resistant rickets due to hypophosphatemia, as noted in this case. Another major feature of cystinosis is growth retardation, often accompanied by delayed bone age as is in our case.