Endocrine Abstracts

Queen’s Medical Centre, Nottingham, United KingdomTyrosinemia type-1 is a rare autosomal recessive disorder. It usually presents in an acute form in early infancy. Rarely, it can also present as a chronic form with gradual onset. The key presenting features are failure to thrive, liver dysfunction and/or Fanconi syndrome. We present a perplexing case of a 2-year-old girl with tyrosinemia type-1, who initially presented with failure to thrive and hypophosphatemic rickets without overt liver dysfunction and required extensive input from oncology, endocrinology, liver, renal and metabolic teams before diagnosis was established. She had an elevated fibroblast growth factor 23 (FGF23) level, which is unexpected as FGF23 would normally be low in Fanconi hypophosphatemia.

Presentation: A 2-year-old girl was acutely referred by her health visitor due to concerns of poor appetite, tiredness, faltering growth, loss of ability to walk independently and progressive bowing of legs discovered during her routine 2-year check.

Examination: Height: 74.1 cm (<0.4th percentile), weight: 8.5 kg (0.4th percentile), bowed legs, rachitic rosary and mild hepatomegaly

Investigations: Urea and electrolytes: normal, Suspected diagnosis: oncogenic osteomalacia Further investigations: MRI abdomen: numerous T2 hypointense lesions, no features of hepatoblastoma/hepatocellular carcinoma Plasma tyrosine level: 533 umol/l (38–160) Urine: increased excretion of succinyl acetone and generalised aminoaciduria Liver biopsy: advanced fibrosis Final diagnosis: tyrosinemia type-1 Treatment: nitisinone, protein restriction, phosphate and calcium supplements and alfacalcidol Currently, she is 10 months post-diagnosis and is again walking independently. FGF23 is high at 128 RU/ml and urine phosphate is still elevated at 33 mmol/l.

Conclusion: FGF23 may have a role in the causation of hypophosphatemia in patients with tyrosinemia, and this merits further investigation.