Estimating the relative frequency of leukodystrophies and recommendations for carrier screening in the era of next‐generation sequencing

Leukodystrophies are a heterogeneous group of heritable disorders characterized by abnormal brain white matter signal on magnetic resonance imaging (MRI) and primary involvement of the cellular components of myelin. Previous estimates suggest the incidence of leukodystrophies as a whole to be 1 in 7,000 individuals, however the frequency of specific diagnoses relative to others has not been described. Next generation sequencing approaches offer the opportunity to redefine our understanding of the relative frequency of different leukodystrophies. We assessed the relative frequency of all 30 leukodystrophies (associated with 55 genes) in more than 49,000 exomes. We identified a relatively high frequency of disorders previously thought of as very rare, including Aicardi Goutières Syndrome, TUBB4A‐related leukodystrophy, Peroxisomal biogenesis disorders, POLR3‐related Leukodystrophy, Vanishing White Matter, and Pelizaeus‐Merzbacher Disease. Despite the relative frequency of these conditions, carrier‐screening laboratories regularly test only 20 of the 55 leukodystrophy‐related genes, and do not test at all, or test only one or a few, genes for some of the higher frequency disorders. Relative frequency of leukodystrophies previously considered very rare suggests these disorders may benefit from expanded carrier screening.     

Metachronous T‐Lymphoblastic Lymphoma and Burkitt Lymphoma in a Child With Constitutional Mismatch Repair Deficiency Syndrome

Constitutional mismatch repair deficiency (CMMRD) is a cancer predisposition syndrome associated with a high risk of developing early‐onset malignancies of the blood, brain, and intestinal tract. We present the case of a patient with T‐lymphoblastic lymphoma at the age of 3 years, followed by Burkitt lymphoma 10 years later. This patient also exhibited numerous nonmalignant findings including café au lait spots, lipomas, bilateral renal nodules, a nonossifying fibroma, multiple colonic adenomas, and a rapidly enlarging pilomatrixoma. The spectrum of malignant and nonmalignant neoplasms in this patient highlights the remarkable diversity, and early onset, of lesions seen in children with CMMRD.     

Ovarian Cancer in BRCA Mutation Carriers: Improved Outcome After Intraperitoneal (IP) Cisplatin

Background

Ovarian cancer arising in women with BRCA mutations is known to have a more favorable outcome and to be more responsive to platinum-based regimens than in those without a hereditary background. We analyze our previously published intraperitoneal (IP) studies in relation to BRCA mutation status and update their outcomes.

Methods

Among 62 patients with ovarian cancer enrolled in IP platinum doublet studies in clinical trials (with etoposide (n = 18), with floxuridine (n = 30), and with topotecan (n = 14)), a deleterious BRCA mutation was eventually identified in 10 patients. The outcomes in these BRCA mutation carriers are described and compared with survival of others in respective trials.

Results

Ten patients that were confirmed to have BRCA mutations—all with high-grade and stages IIC to IV disease—survived a median of 10 years (range: 4–18+) after receiving IP cisplatin-based regimens. Two continue with no evidence of disease since their IP treatment, while four others remain alive with recurrences after 8, 9, 10, and 11 years, respectively.

Conclusions

This experience suggests that IP cisplatin leads to favorable long term outcomes in advanced ovarian cancer in women with defective homologous recombination (i.e., with deleterious BRCA mutations). Whether such cisplatin dose-intensification from IP relative to (intravenous) IV drug administration leads to superior results in these mutation carriers requires further study.