Rare PHEX variant with insidious presentation leads to a delayed diagnosis of X-linked hypophosphatemia.

A 7-year-old girl without a significant previous medical history was diagnosed with X-linked hypophosphatemic rickets (XLHR) due to a rare, most likely pathogenic, PHEX gene variant after a 4-year delayed diagnosis due to mild clinical presentation. At 2 years of age, her intoeing and femoral bowing were attributed to physiologic bowing and borderline vitamin D sufficiency, despite phosphorus not being measured. Hypophosphatemia was eventually detected after incomplete improvement of bowing and leg length discrepancy with suboptimal linear growth. This rare PHEX variant (c.1949T>C, p.Leu650Pro) further supported the clinical diagnosis of XLHR. Treatment with burosumab (an anti-FGF23 monoclonal antibody) normalised phosphorus and alkaline phosphatase levels and improved her bowing. The diverse phenotypic presentation of this variant can result in delayed diagnosis and highlights the importance of prompt assessment of phosphorus levels in patients with skeletal deformities to ensure timely recognition and treatment.

Primary renal diffuse large B-Cell lymphoma causing haemodialysis-dependent nephromegaly in a child.

A 4-year-old boy presented with fatigue and was found to have severe kidney injury requiring haemodialysis. A renal ultrasound demonstrated bilateral nephromegaly with mild loss of corticomedullary differentiation but preserved echogenicity. He had a persistent isolated monocytosis. Renal biopsy revealed extensive infiltration by primary renal diffuse large B-cell lymphoma. He required haemodialysis for 18 days and received chemotherapy with cyclophosphamide, doxorubicin, vincristine, prednisone, rituximab and intrathecal methotrexate. He achieved remission with an estimated glomerular filtration rate of 50 mL/min/1.73 m2, and his kidneys returned to normal size. Nephromegaly due to renal-limited haematolymphoid disease is extremely rare, especially in children.