Joyce Emily, Ho Jacqueline, El-Gharbawy Areeg, Salgado Cláudia M, Ranganathan Sarangarajan, Reyes-Múgica Miguel
1 Division of Nephrology, Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.
2 Division of Medical Genetics, Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.
Pediatr Dev Pathol. 2017 Jan-Feb;20(1):72-75. doi: 10.1177/1093526616683873.
Cystinosis is the most common cause of inherited renal Fanconi syndrome in young children, and typically presents with laboratory findings of a proximal tubulopathy and corneal crystals by one year of age. We describe here renal biopsy findings in a 20-month-old patient with an atypical presentation of distal renal tubular acidosis, diabetes insipidus, and the absence of corneal crystals. Although renal biopsy is usually not necessary to establish the diagnosis of cystinosis, when the patient presents with atypical signs and symptoms, a renal biopsy may be extremely valuable. A 20-month-old boy presented with failure to thrive, polyuria, polydipsia, and rickets. He initially showed evidence of a renal tubular acidosis, mild renal insufficiency, and nephrogenic diabetes insipidus. His initial ophthalmologic examination did not demonstrate corneal crystals. His subsequent workup revealed phosphaturia, suggesting a partial proximal tubulopathy. Concomitantly, a renal biopsy revealed prominent podocytes with an immature glomerular appearance, and electron microscopy analysis showed numerous intracellular crystals within tubular epithelial cells. Subsequent laboratory and genetic testing confirmed a diagnosis of infantile nephropathic cystinosis. This case highlights the variability in the clinical presentation of cystinosis, resulting in an uncommon clinical picture of a rare disease. Given that treatment is available to prolong renal function and minimize the extra-renal manifestations of this disorder, early diagnosis is essential. It is important to raise the index of suspicion of cystinosis by recognizing its subtle morphological changes in young patients, and that nephrogenic diabetes insipidus can be secondary to this disorder.
胱氨酸病是幼儿遗传性范科尼综合征最常见的病因，通常在1岁时出现近端肾小管病变和角膜晶体的实验室检查结果。我们在此描述一名20个月大患者的肾活检结果，该患者表现为非典型的远端肾小管酸中毒、尿崩症且无角膜晶体。虽然通常无需肾活检来确诊胱氨酸病，但当患者出现非典型体征和症状时，肾活检可能极具价值。一名20个月大的男孩出现生长发育迟缓、多尿、烦渴和佝偻病。他最初表现出肾小管酸中毒、轻度肾功能不全和肾性尿崩症的证据。他最初的眼科检查未发现角膜晶体。随后的检查发现有磷尿症，提示部分近端肾小管病变。同时，肾活检显示足细胞突出，肾小球外观不成熟，电子显微镜分析显示肾小管上皮细胞内有大量细胞内晶体。随后的实验室和基因检测证实诊断为婴儿型肾病性胱氨酸病。该病例突出了胱氨酸病临床表现的变异性，导致一种罕见疾病出现不常见的临床表现。鉴于有治疗方法可延长肾功能并使该疾病的肾外表现最小化，早期诊断至关重要。通过识别年轻患者中其细微的形态学变化来提高对胱氨酸病的怀疑指数很重要，而且肾性尿崩症可能继发于该疾病。
