无色素性黑素瘤是一种罕见的黑素瘤形式，占据所有黑素瘤病例的2%-8%。在人类群体中，患有三体21综合征的患者患黑素瘤的发病率相对未知。据理论推测，多余的21号染色体副本对黑素瘤的发展起着保护作用，因为患有三体21综合征的人也携带该染色体上的额外基因副本，其中可能包括抗癌基因。文献回顾发现至今为止有四例三体21综合征患者出现皮肤黑素瘤的报道。据作者所知，这是第一例三体21综合征患者出现无色素性黑素瘤的病例，也是第五例三体21综合征患者患黑素瘤的报道。这个病例突出了对所有疑似诊断不明的新皮肤病变进行专科转诊的必要性。© BMJ Publishing Group Limited 2023. 未经许可，不得进行商业再利用。由BMJ出版。

Amelanotic melanoma is an uncommon form of melanoma; accounting for 2%-8% of all melanoma cases. In the human population, the incidence of melanoma in patients with trisomy 21 is relatively unknown. It is theorised that having an extra copy of chromosome 21 is protective against melanoma development as people with trisomy 21 also carry an extra copy of the genes on that chromosome including any that protect against cancer. A literature review revealed four other reported cases of cutaneous melanoma in persons with trisomy 21. To the authors' knowledge, this is the first case of amelanotic melanoma presenting in a patient with trisomy 21 and the fifth case of melanoma overall reported in a patient with trisomy 21.This case highlights the need for specialist referral of all new skin lesions where the diagnosis is unclear.© BMJ Publishing Group Limited 2023. No commercial re-use. See rights and permissions. Published by BMJ.