Co-Occurrence of Achondroplasia and 16p11.2 Deletion Syndrome in a Child With Group 4 Medulloblastoma: Expanding the Spectrum of Dual Genetic Diagnoses.
Hua Wang
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Case in brief
A 13-year-old male with genetically confirmed achondroplasia (FGFR3 c.1138G > A) and a de novo 16p11.2 microdeletion developed metastatic Group 4 medulloblastoma at age 12, with leptomeningeal dissemination (M3). The tumor was non-WNT/non-SHH. Despite resection, craniospinal irradiation, and combination chemotherapy, it recurred and progressed; the patient died at age 13.
What made this case unusual
The report describes co-occurring achondroplasia and 16p11.2 deletion in a child with Group 4 medulloblastoma. Neither condition is established as independently conferring risk for this tumor, although both affect MAPK/ERK signaling, a pathway implicated in Group 4 medulloblastoma biology.
Diagnostic / clinical pearl
When a patient has multiple genetic diagnoses, consider and document multilocus pathogenic variation; the authors note that developmental and oncogenic signaling interactions warrant further investigation.