DISCUSSION
There is no standard treatment for advanced-stage HLRCC-related RCC. However, most cases are diagnosed in advanced stages with dismal prognosis.3, 6 It is strongly recommended that the HLRCC patients’ relatives receive genetic counseling and FH gene mutation screening. For confirmed HLRCC patients with FH gene mutation, the RCC surveillance program should start at 8–10 years old based on the age of the youngest case to date.4 Here, we report a case of a boy who developed HLRCC-related RCC at 7 years old, which may affect the starting age of the future RCC-surveillance program for patients with HLRCC.
A clear association between FH gene mutation and renal cyst formation has been confirmed in mouse model.7Consistent with the mouse model phenotype, the prevalence of renal cysts in patients with HLRCC has been reported to be significantly higher than that in the normal population,8 reaching 45%–50% in adult cases.3, 9 Although it is controversial that HLRCC carrier with renal cyst developed kidney cancer more frequently than without cyst,9 pathological examination of resected renal cysts of HLRCC patients revealed positive 2-succinyl-cysteine immunostaining,10 suggesting a complete loss of function of the FH gene in renal cysts of HLRCC patients because of somatic genetic events. In the present case, the small solid lesions of RCC were located in the right renal cystic region. Renal cysts in these HLRCC patients may be precancerous lesions and should be carefully observed.
The present case was initially misdiagnosed with MCDK because of multiple renal cysts noted on an enhanced CT scan. Although it is rare, renal cyst formation can be seen in children with HLRCC.11 HLRCC should be considered an important differential diagnosis for children with multiple renal cystic lesions and many other genetic disorders, including MCDK, Von Hippel–Lindau syndrome, or tuberous sclerosis.
In conclusion, we present a 7-year-old patient with HLRCC-related RCC with multiple renal cystic lesions. Since this is the youngest reported case to date, this report may affect the starting age for future RCC-surveillance programs for patients with HLRCC.