Two cases of Lowe syndrome presenting as increased fetal nuchal translucency

The oculocerebrorenal syndrome of Lowe: an update

The oculocerebrorenal syndrome of Lowe is a rare X-linked multisystemic disorder characterized by the triad of congenital cataracts, intellectual disability, and proximal renal tubular dysfunction. Whereas the ocular manifestations and severe muscular hypotonia are the typical first diagnostic clues apparent at birth, the manifestations of incomplete renal Fanconi syndrome are often recognized only later in life. Other characteristic features are progressive severe growth retardation and behavioral problems, with tantrums. Many patients develop a debilitating arthropathy. Treatment is symptomatic, and the life span rarely exceeds 40 years. The causative oculocerebrorenal syndrome of Lowe gene (OCRL) encodes the inositol polyphosphate 5-phosphatase OCRL-1. OCRL variants have not only been found in classic Lowe syndrome, but also in patients with a predominantly renal phenotype classified as Dent disease type 2 (Dent-2). Recent data indicate that there is a phenotypic continuum between Dent-2 disease and Lowe syndrome, suggesting that there are individual differences in the ability to compensate for the loss of enzyme function. Extensive research has demonstrated that OCRL-1 is involved in multiple intracellular processes involving endocytic trafficking and actin skeleton dynamics. This explains the multi-organ manifestations of the disease. Still, the mechanisms underlying the wide phenotypic spectrum are poorly understood, and we are far from a causative therapy. In this review, we provide an update on clinical and molecular genetic findings in Lowe syndrome and the cellular and physiological functions of OCRL-1.

Lowe syndrome: a single center's experience in Korea

Purpose

Lowe syndrome is a rare, X-linked recessive disorder caused by mutations in the OCRL gene. It involves multiple anatomic systems, particularly the eyes, central nervous system, and kidneys, and leads to profound growth failure and global developmental delay. This study evaluated the clinical and genetic characteristics of Korean patients with Lowe syndrome.

Methods

The clinical findings and results of genetic studies were reviewed for 12 male patients diagnosed with Lowe syndrome at a single medical institution.

Results

The mean age of the patients at presentation was 2.2 months (range, 0-4 months), although the diagnosis was delayed by a mean of 2.8 years (range, 0-9.7 years). The mean follow-up period was 9.0 years (range, 0.6-16.7 years). Nine mutations in OCRL were identified in 11 patients (92%), with three novel mutations. The main presentation was congenital cataract in both eyes necessitating early cataract removal in the 11 patients with impaired visual acuity. Profound short stature and developmental delay were observed in all patients, and seizures occurred in 50% of the patients. All patients suffered from proximal renal tubular dysfunction, and one patient developed chronic renal failure. Other manifestations included pathologic fracture (50%), cutaneous cysts (42%), and cryptorchidism (42%). However, there was no bleeding tendency, and none of the patients died during the study period.

Conclusion

This study describes the clinical and genetic characteristics of Korean patients with Lowe syndrome. The observations are helpful for understanding the natural courses of Lowe syndrome and for appropriate genetic counseling.