The Importance of the Early Diagnosis of Infantile Nephropathic Cystinosis: A Case Report

Introduction

Cystinosis is a rare autosomal recessive lysosomal storage disease characterized by defective transport of the aminoacid cystine across the lysosomal membrane leading to lysosomal accumulation of cystine in many organs, mainly kidneys and eyes (Nesterova & Gahl, In GeneReviews, 2017; Servais et al., Clin J Am Soc Nephrol, 2008; 3: 27–35). The annual incidence of cystinosis is 1 in 100,000–200,000 live births in the United States and Europe (Gahl et al., N Engl J Med. 2002; 347: 111–121). All forms of cystinosis are caused by mutations in the CTNS gene that maps to chromosome 17p13 and encodes for a lysosomal membrane protein, cystinosin which is expressed in all tissues acting as a cystine transporter. More than 100 mutations have been reported. Large deletions or point mutations in critical aminoacids cause infantile cystinosis, while milder mutations that do not disrupt the reading frame are observed in late-onset and ocular forms (Kalatzis et al., Hum Mutat 2002; 20: 439–446; Papizh et al., BMC Nephrology 2019; 20: 400).

Three clinical types of cystinosis have been described based on the age of presentation and the degree of renal disease severity: infantile nephropathic form; late-onset adolescent form (intermediate form or juvenile nephropathic form); and benign adult form (non-nephropathic form or ocular non-nephropathic form) (Gahl et al., N Engl J Med. 2002; 347: 111–112, Servais et al., Clin J Am Soc Nephrol, 2008; 3: 27–35). The most common form (95%) is infantile nephropathic form and presents with Fanconi syndrome and progression to end-stage kidney disease (ESKD) in the first decade of life (Gahl et al., N Engl J Med. 2002; 347: 111–112). Juvenile form is usually diagnosed later in childhood/adolescence with symptoms of mild renal disease (Servais et al., Clin J Am Soc Nephrol, 2008; 3: 27–35). Ocular form is characterized by corneal cystine crystal depositions without renal involvement (Gahl et al., N Engl J Med. 2002; 347: 111–112)

Here we report a case with the infantile nephropathic cystinosis revealed by glycosuria at the age of 4 months.

Publication History

Article published online:
13 July 2020