Surucu Kara Ilknur, Oncul Ummuhan, Kose Engin, Turan Husnu Mutlu, Ceylan Ahmet Cevdet, Eminoglu Fatma Tuba
Department of Pediatric Metabolism, Faculty of Medicine, Ankara University, Ankara, Turkey.
Department of Medical Genetics, Ankara City Hospital, Ankara, Turkey.
Mol Syndromol. 2022 May;13(3):240-245. doi: 10.1159/000520502. Epub 2022 Feb 3.
Hypotonia-cystinuria syndrome is a contiguous gene deletion syndrome that is characterized by hypotonia, developmental delay, and cystinuria type A. We present a male patient who was admitted to our center with clinical findings of hypotonia-cystinuria syndrome and diagnosed with megaconial congenital muscular dystrophy and cystinuria.
A 16-month-old male patient was admitted with complaints of restlessness and body laxity. It was stated that the patient had hypotonia and growth retardation at the age of 2 months. Physical examination revealed mild hypotonia, growth retardation, and development delay, while laboratory examinations identified elevated serum creatine kinase and elevated dibasic amino acid in urine analysis. Because of the findings of hypotonia, growth retardation, developmental delay, and cystinuria, hypotonia-cystinuria syndrome was considered as a differential diagnosis. However, by chromosomal microarray no contiguous deletion in region 2p21 was found, while a novel homozygous c.225-2A>T pathogenic variant in the gene and a c.1266_1267delGT heterozygous variant in the gene inherited from the mother were identified with whole-exome sequencing. The co-occurrence of megaconial congenital muscular dystrophy and cystinuria, mimicking hypotonia-cystinuria syndrome, was confirmed.
This case suggests that in countries with a high frequency of consanguineous marriage, even if the molecular genetic analysis results are not compatible with the clinical findings, it should be kept in mind that different genetic diseases may coexist.
肌张力减退 - 胱氨酸尿症综合征是一种连续性基因缺失综合征，其特征为肌张力减退、发育迟缓以及A型胱氨酸尿症。我们报告一名男性患者，他因肌张力减退 - 胱氨酸尿症综合征的临床表现入院，最终被诊断为大孢子先天性肌营养不良和胱氨酸尿症。
一名16个月大的男性患者因烦躁不安和身体松弛前来就诊。据描述，该患者在2个月大时就出现了肌张力减退和生长发育迟缓。体格检查发现轻度肌张力减退、生长发育迟缓以及发育延迟，实验室检查显示血清肌酸激酶升高，尿液分析中二元氨基酸升高。鉴于肌张力减退、生长发育迟缓、发育延迟和胱氨酸尿症的表现，肌张力减退 - 胱氨酸尿症综合征被列为鉴别诊断。然而，通过染色体微阵列分析未发现2p21区域的连续性缺失，而全外显子测序确定了该基因中一个新的纯合c.225 - 2A>T致病变异以及从母亲遗传而来的该基因中的一个c.1266_1267delGT杂合变异。大孢子先天性肌营养不良和胱氨酸尿症同时出现，酷似肌张力减退 - 胱氨酸尿症综合征，这一诊断得到了证实。
该病例表明，在近亲结婚频率较高的国家，即使分子遗传学分析结果与临床表现不相符，也应牢记不同的遗传疾病可能同时存在。
