Declining free thyroxine levels over time in irradiated childhood brain tumor survivors

Objective: The incidence of cranial radiotherapy (cRT)–induced central hypothyroidism (TSHD) in childhood brain tumor survivors (CBTS) is reported to be low. However, TSHD may be more frequent than currently suspected, as its diagnosis is challenging due to broad reference ranges for free thyroxine (FT4) concentrations. TSHD is more likely to be present when FT4 levels progressively decline over time. Therefore, we determined the incidence and latency time of TSHD and changes of FT4 levels over time in irradiated CBTS. Design: Nationwide, 10-year retrospective study of irradiated CBTS. Methods: TSHD was defined as ‘diagnosed’ when FT4 concentrations were below the reference range with low, normal or mildly elevated thyrotropin levels, and as ‘presumed’ when FT4 declined ≥ 20% within the reference range. Longitudinal FT4 concentrations over time were determined in growth hormone deficient (GHD) CBTS with and without diagnosed TSHD from cRT to last follow-up (paired t-test). Results: Of 207 included CBTS, the 5-year cumulative incidence of diagnosed TSHD was 20.3%, which occurred in 50% (25/50) of CBTS with GHD by 3.4 years (range, 0.9–9.7) after cRT. Presumed TSHD was present in 20 additional CBTS. The median FT4 decline in GH-deficient CBTS was 41.3% (P < 0.01) to diagnosis of TSHD and 12.4% (P = 0.02) in GH-deficient CBTS without diagnosed TSHD. Conclusions: FT4 concentrations in CBTS significantly decline over time after cRT, also in those not diagnosed with TSHD, suggesting that TSHD occurs more frequently and earlier than currently reported. The clinical relevance of cRT-induced FT4 decline over time should be investigated in future studies

Heterophilic antibodies leading to falsely positive D-dimer concentration in an adolescent

BACKGROUND: We present the case of a 15-year-old adolescent with suspected pulmonary embolism and repeatedly elevated D-dimer levels. KEY CLINICAL QUESTION: We aim to determine the cause for elevated D-dimer levels in a patient without venous thromboembolism. CLINICAL APPROACH: When the D-dimer measurement was repeated with different assays, D-dimer levels were within the normal reference interval. Dilution series with assay diluent or low-affinity antibody blocking reagents either did not or only partially decreased the D-dimer value using the original reagent kit. CONCLUSION: Analyses suggested the presence of interfering heterophilic antibodies in patient plasma, a known phenomenon with immunoturbidimetric D-dimer assays, which is rarely described. Prior to drawing this conclusion, the patient underwent extensive diagnostic testing, which led to uncertainty and discomfort for the health care providers, the patient, and their family

Solitary juvenile xanthogranuloma of the temporal muscle and bone penetrating the dura mater in a 2-month-old boy: case report

Juvenile xanthogranuloma (JXG) is a rare histiocytic disorder primarily observed during the first 2 years of life. Most patients present with a solitary cutaneous lesion: however, others present with extracutaneous manifestations or even with systemic involvement. The authors describe a 2-month-old boy in whom was diagnosed a unifocal extracutaneous JXG involving the temporal bone. Unlike 3 other cases of solitary JXGs of the temporal bone in the literature. the present case involved destruction of the dura mater and leptomeningeal enhancement surrounding the entire temporal lobe. The lesion did not regress after an initial biopsy procedure and had to be removed more radically because of progressive mass effect on the brain. The child recently underwent a reconstructive skull procedure and is doing well almost 2 years postoperatively without evidence of disease. This case demonstrates that even in instances of extensive disease a favorable outcome is possible without chemotherapy