Liddle Syndrome due to a Novel c.1713 Deletion in the Epithelial Sodium Channel ß-Subunit in a Normotensive Adolescent.

OBJECTIVE: Liddle syndrome (LS) is a rare autosomal dominant condition secondary to a gain-of-function mutation affecting the epithelial sodium channels (ENaCs) in the distal nephron. It presents with early-onset hypertension, hypokalemia, and metabolic alkalosis in the face of hyporeninemia and hypoaldosteronism. We report a novel mutation affecting the ENaCs in a normotensive adolescent with LS. METHODS: We describe a pediatric case of LS with a novel mutation and review the condition's presentation and management. To date, 31 different mutations in the ß- or γ-subunit of ENaCs have been reported as associated with LS. RESULTS: We describe a 16-year-old girl presenting with muscle cramps with a strong family history of hypertension and hypokalemia. Initial investigations revealed hypokalemia together with hypoaldosteronism and hyporeninemia. Subsequent genetic testing revealed a novel mutation in SCNN1B (deletion: c.1713delC), leading to the premature termination of the sodium channel epithelial 1 subunit-ß protein and the LS phenotype. Treatment with triamterene (50 mg, twice daily) and potassium chloride (20 mEq, once daily) normalized the serum potassium and led to resolution of her muscle cramps. CONCLUSION: It is essential to consider investigating the presence of rare genetic syndromes, like LS, when a patient presents with hypokalemia. Further studies are needed to understand the variable presentation of this condition.

Diagnostic Utility of Isolated Tube C Positivity in T-Cell Receptor ß Testing Using BIOMED-2 Primers.

OBJECTIVES: T-cell receptor (TCR) gene rearrangement studies are widely used for assessing T-cell clonality. The frequency and significance of clonal peaks restricted to TCR ß (TCRB) tube C are uncertain. We retrospectively reviewed 80 TCR studies performed on bone marrow/peripheral blood. METHODS: TCRB and TCR γ (TCRG) analyses were performed using BIOMED-2 primers. A peak was considered clonal or atypical if it was reproducible and 5× or more or 3× to 5× polyclonal background, respectively. RESULTS: TCRB analysis demonstrated 12 (15%) of 80 cases with one to four isolated peaks in tube C (>3×) with polyclonal pattern in tubes A and B. TCRG analysis was monoclonal in two cases (both definite T-cell neoplasms), polyclonal in four, and oligoclonal in six. Of the 10 cases without clone in TCRG, six had autoimmune disorder and none had T-cell neoplasm. CONCLUSIONS: Peaks restricted to TCRB tube C in the TCR analysis may be misleading, as it is often not indicative of an overt T-cell neoplasm.