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Hemophagocytic lymphohistiocytosis (HLH) is a syndrome of severe immune dysregulation that encompasses a broad range of underlying genetic diseases and infectious triggers. Monogenic conditions, autoimmune diseases, and infections can all drive the phenotype of HLH and associated immune hyperactivation with hypercytokinemia. A diagnosis of HLH usually requires a combination of clinical and laboratory findings; there is no single sensitive and specific diagnostic test, which often leads to "diagnostic dilemmas" and delays in treatment initiation. Ferritin levels, one of the most commonly used screening tests, were collected across a large tertiary care pediatric hospital to identify the positive predictive value for HLH. Herein, we present several cases that illustrate the clinical challenges of confirming an HLH diagnosis. Additionally, we report on the utility of establishing a formal multi-disciplinary group to aid the prompt diagnosis and treatment of patients presenting with HLH-like pathophysiologies., (© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Background: The present study was designed to determine the reliability of the current practice of random pre-dialysis phosphate testing in subjects receiving hemodialysis therapy, since phosphate levels exhibit a significant variation in a 24-hour period under usual physiologic conditions., Methods: Subjects receiving chronic hemodialysis (HD) were invited to participate during an incidental hospitalization. In Study A subjects (n=31) had serum phosphate tested three times on a single non-dialysis day, between 6 to 7 am (A1), between 11 am to 12:30 pm (A2), and 3:45 pm to 4:45 pm (A3). In study B subjects (n=25) had serum phosphate tested just before (B1) and 2 hours after lunch (B2), on a non-dialysis day. For Study A the collection times coincided with the start times of the out-patient dialysis shifts at our institution. All patients continued their usual phosphate binder therapy, if any. For study A the results were analyzed using one-way repeated measures analysis of variance or Friedman repeated measures analysis of variance on ranks, as opposite. Paired t-test was used for Study B. Results are expressed as mean+/- standard deviation., Results: Twenty-three men and eight women (mean age 62.2+/-15.2 years) were enrolled in Study A (24 Caucasian, 7 African-American). Nineteen men and six women (mean age 65.5+/-12.8 years) participated in study B (19 Caucasian, 6 African-American). In Study A, there was no significant difference in the mean serum phosphate levels in the samples collected through the day A1 (4.5+/-1.3 mg/dL), A2 (4.5+/-1.3 mg/dL) and A3 (4.7+/-1.5 mg/dL) (p=0.19 for comparison of the three). The mean amplitude of circadian variation (peak minus trough) was 0.64+/- 0.37 mg/dL. Similarly, there was no significant difference in the mean serum phosphate before (4.4+/-1.4 mg/dL) and two hours after lunch (4.4+/-1.5 mg/dL) (p =0.6). The mean of the difference in serum phosphate (post-prandial minus pre-prandial) was 0.2+/-0.4 mg/dL., Conclusion: Our results in hospitalized HD subjects indicate there is no significant difference in phosphate levels at different times of a single day or in relation to meals.