Renal complications in two patients with dentatorubral-pallidoluysian atrophy

The relationship between the number of CAG repeats and clinical manifestations: a survey of Chinese DRPLA family

OBJECTIVE

To describe the clinical, radiological, and genetic characteristics of a Chinese family with dentatorubropallidoluysian atrophy (DRPLA). Explore the distribution of CAG repeat size to the clinical features of patients.

METHODS

We collected the clinical symptoms and DNA analysis for the DRPLA gene was performed on the family members. DRPLA patients reported in the literature were reviewed to analyze the association between CAG repeat size and clinical features.

RESULTS

Six family members were confirmed by genetic analysis. The number of CAG repeat in the proband, her sister, her grandmother, her father, her uncle, and her cousin, was determined respectively as 63, 75, 50, 50, 50, 54. In our family, the sister of the proband had the earliest onset age and the most severe clinical symptoms, followed by the proband, and other family members showed no obvious clinical symptoms. Consistent with the conclusion of previous studies, the more repeats CAG, the earlier the age of onset and the severer phenotypes are.

CONCLUSION

We found six family members have CAG repeat expansion in the DRPLA gene on chromosome 12p13. Even in the same family, patients have different clinical presentations. The size of CAG repeats is negatively correlated with the age of onset and positively correlated with symptom severity. When the number of repeats is ≥ 63, the age at onset is < 21 years old, and obvious clinical symptoms generally appear. It seems to say the more repeats CAG, the earlier the age of onset and the severer phenotypes are.

LIMITATIONS

With a small number of cases in our family, the conclusion that the more CAG repeats, the earlier the onset and the more severe the clinical symptoms cannot be fully proved.

Hypoalbuminemia in early onset dentatorubral-pallidoluysian atrophy due to leakage of albumin in multiple organs

We delineate a complication of hypoalbuminemia in dentatorubral-pallidoluysian atrophy (DRPLA), which we have found to be common in this disorder. In addition, we explored the pathogenesis of this phenomenon through clinical and histological examinations. Clinical course and laboratory findings of nine patients with childhood-onset DRPLA (aged 6-49 years; CAG repeat length 62-93) were retrospectively reviewed. Autopsied specimens from three patients were examined by histopathological and immunohistochemical analyses. Eight DRPLA patients showed hypoalbuminemia <3.5 g/dl in the initial stages of the disease (age, 2-32 years), which correlated with the CAG repeat length in each patient. Disease worsened in six patients, often triggered by febrile infections and accompanied by increased urinary protein excretion. One patient showed increased fecal α1-antitripsin while another showed accumulation of radioactive albumin in the urinary and gastrointestinal tracts after intravenous infusion. Immunohistochemistry revealed albumin-containing monocytes and astrocytes in the perivascular areas of the cerebral white matter. Fluid collection in the glomerular capillaries was noted. Immunolabeling using antibodies against the expanded polyglutamine (polyQ) polypeptide was positive in cerebral cortical neurons, hepatocytes, renal collecting ducts, and glomerular podocytes, which act as filtration barrier against serum proteins. Serum albumin appears to easily leak from blood vessels in certain visceral organs in DRPLA during later stages of the illness, particularly in the kidneys of patients with largely expanded CAG repeats. We hypothesize that the accumulation of the DRPLA gene product with expanded polyQ sequences in the podocytes results in the dysfunction of the glomerular filtration barrier.