This case involved a 6-year-old girl. Her fingers became purple in the winter a year before admission. The finger discoloration improved, but the finger swelling continued. Hardening of the skin was observed on her abdomen and upper arms three months before admission. One month before admission, she exhibited mild dyspnea when going up a hill. A collagen disease was suspected because of these symptoms and high anti nuclear antibody titer by her family doctor. She was then admitted to our hospital.
 On admission, she had a high titer of anti Scl-70 antibody and ground glass opacity in the lung near the pleura on chest high resolution CT (HRCT), indicating interstitial lung disease. We diagnosed systemic sclerosis because she also had generalized skin hardening and a digital ulcer on her big toe.
 We used steroid pulse therapy followed by cyclophosphamide pulse therapy for interstitial lung disease and generalized skin hardening. We also used Ca blockers and bosentan for the digital ulcer and Raynaud’s phenomenon. The digital ulcer markedly improved after starting bosentan treatment. Juvenile systemic sclerosis is very rare, and we report here her clinical course with a review of the literature.

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 One of the multivariate analyses commonly used in medical research is logistic regression. It is designed to predict from explanatory variables (covariates) the probability of binary (nominal) outcomes (P), such as survival or death and positive or negative response to a test drug, using a logistic regression model, where log (P /(1-P)) is assumed to be a linear combination of covariates (b₀ + b ₁ x₁ + b ₂ x₂ ...).
  In non-randomized retrospective studies, the results of these analyses may be biased by confounding factors. To adjust for the confounders, a propensity score analysis using logistic regression has been proposed, permitting us to abridge multiple confounders to a single composite variable. This concept and technique are herein explained.

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 We established a system to easily estimate renal function, and a system to record the time from medication intake to testing using prothrombin time (PT) and activated partial thromboplastin time (aPTT) data in order to estimate the anti-coagulation effects in patients administered direct oral anticoagulants (DOACs). DOACs are contraindicated in patients who have severely impaired renal function due to their high renal excretion rates. The creatinine clearance rate (CCr), calculated using the Cockcroft-Gault formula, was adopted as the formal estimate of renal function in patients administered DOACs. In comparison with the estimated glomerular filtration rate (eGFR), the CCr tends to be lower in elderly patients with small physiques, who comprise a sizeable proportion of the population in Japan. Therefore, the CCr should be used instead of the eGFR value. We introduced the CCr in our laboratory system in order to determine which patients are contraindicated due to renal impairment and to follow-up the renal function of the patients periodically. Although DOACs are available for administration with a fixed dose and require no monitoring of their anti-coagulation effects, assessment of the anti-coagulant effects is desirable in patients at high risk of bleeding. Furthermore, the laboratory data vary depending on the time from drug intake to examination due to the short half-life of DOACs. In our hospital, the medical technologists record the time of intake when they collect blood from the patients, and this information is subsequently listed in the laboratory data reports. Thus, the risk of DOAC administration is managed by estimating the PT or aPTT while considering the time to testing from medication intake.

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 Thrombotic thrombocytopenic purpura (TTP) is characterized by markedly reduced activity of ADAMTS13, which is a plasma protease that regulates the function of von Willebrand factor (VWF) by cleaving ultra large VWF (UL-VWF) into smaller multimers. Deficiency of ADAMTS13 activity results in increased levels of circulating UL-VWF, which induces the generation of platelet thrombi in the microvasculature, thereby causing microangiopathic hemolytic anemia, consumptive thrombocytopenia, and ultimately, organ ischemia. TTP can be classified into hereditary TTP, which is caused by homozygous or compound heterozygous inactivating mutations of ADAMTS13, and acquired TTP, which is caused by the development of inhibitory autoantibodies against ADAMTS13. The mainstay of management for patients with acquired TTP is plasma exchange (PEx), the aim of which is to remove circulating inhibitors and replace the deficient ADAMTS13 enzyme. PEx has been shown to reduce the mortality rate of patients from 90% prior to the introduction of PEx, to approximately 20% after its introduction. However, PEx can induce enhanced immunological responses to the infused plasma containing ADAMTS13, leading to the ‘inhibitor rebound’ phenomenon shortly after the initiation of PEx. Other treatments include high-dose steroids and rituximab; the former suppresses production of ADAMTS13 autoantibodies and the latter, which is a chimeric monoclonal antibody against the CD20 antigen expressed on B lymphocytes, leads to high-rate and sustainable remission.

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