Purpose: Vitelliform Macular Dystrophy is an inherited autosomal dominant disease with variable expressivity, caused by a mutation in the BEST1 gene. We report a family with variable expressivity and incomplete penetrance in its members.

Materials and Methods: A Mexican family was studied. It was comprised of six individuals (father, mother, and four children). A clinical history was taken, and a complete ophthalmological examination (distance best-corrected visual acuity, slit-lamp biomicroscopy, optical coherence tomography, fundus autofluorescence, optical coherence tomography angiography, and electrophysiological studies) was performed in each individual.

Results: Two members presented low visual acuity and vitelliform lesions in different stages in the ocular fundus. The assessment suggested a diagnosis of Vitelliform Macular Dystrophy. Genetic analysis was performed by sequencing of exons 2, 4, 5, 7, 8, and 9 of the BEST1 gene. All patients were carriers of the A variant allele of SNP rs1109748 located in exon 2 (c.219 C > A; p.Ile73=). Also, a missense mutation was identified in exon 7 in the mother and two children (c.851A>G; p.Tyr284Cys). The mother has a normal visual acuity, no abnormal findings in the ophthalmological examination and an abnormal electrooculogram, exhibiting incomplete penetrance.

Conclusion: This represents one of the few cases of Vitelliform Macular Dystrophy with incomplete penetrance, being the first in our country and Latin America, and with our reported mutation with this characteristic.

目的：线形黄斑营养不良是一种遗传性常染色体显性遗传疾病，具有可变的表达能力，是由BEST1基因突变引起的。我们报告了一个家庭，其成员的表达能力和外在表现不完全。

材料与方法：研究了一个墨西哥家庭。它由六个人（父亲，母亲和四个孩子）组成。记录临床病史，并对每个人进行完整的眼科检查（距离最佳矫正视力，裂隙灯生物显微镜，光学相干断层扫描，眼底自发荧光，光学相干断层扫描血管造影和电生理检查）。

结果：两名成员在眼底不同阶段呈现低视力和玻璃状病变。评估提示诊断为黄粉状黄斑营养不良。通过对BEST1基因的外显子2、4、5、7、8和9进行测序，进行遗传分析。所有患者均为外显子2中SNP rs1109748的A变异等位基因的携带者（c.219 C> A； p.Ile73 =）。另外，在母亲和两个孩子的第7外显子中发现了一个错义突变（c.851A> G； p.Tyr284Cys）。母亲的视力正常，眼科检查未见异常，眼电图也未见异常，外pen不完全。

结论：这是少数不完全外显的黄斑状黄斑营养不良的病例之一，在我国和拉丁美洲是首例，并且据我们报道具有这种特征。