Mycoplasma pneumoniae (Mp) sometimes causes immunological complications in children. We present a rare case of hemophagocytic syndrome (HPS) caused by Mp in a previously healthy 7-year-old Japanese girl. A chest radiograph obtained to evaluate the source of her fever showed infiltration in the lower right lung with mild splenomegaly. We could diagnose the patient with HPS on the basis of the hemophagocytic-lymphohistiocytosis- (HLH) 2004 criteria. She met the criteria for fever, splenomegaly, neutrophil count (<1,000/μL), platelet count (<10.0 × 104/μL), fasting triglyceride level (>265 mg/dL), and ferritin level (>500 ng/mL). Furthermore, a peripheral blood smear showed an increased number of monocytes/macrophages with erythrophagocytosis. Treatment with clarithromycin and prednisolone, which was initiated soon after the diagnosis, was successful. Mp infection might partly progress to HPS in certain conditions. Clinicians should be aware of HPS caused by Mp and start appropriate treatment as soon as possible if the disease is suspected.

Elevated serum alkaline phosphatase (ALP) is sometimes observed in children during routine blood chemistry analysis or in patients with various illnesses, and returns to normal within several months. This condition is known as benign transient hyperphosphatasemia (TH). 1-3 TH is considered to be present when serum ALP is >1000 IU/L; 1 furthermore, the elevation is often accompanied by elevation of both liver and bone ALP isoenzymes. 4,5 We report the case of an infant with Epstein-Barr virus (EBV)-associated TH (EBVATH).A male infant was found to have hepatomegaly at his routine health check-up at 18 months of age, and was referred to hospital by his physician. On physical examination, he was in good general condition, but the liver was palpable 5 cm below the right costal margin, and the spleen was enlarged to 3 cm below the left costal margin. Laboratory findings were as follows: white blood cell count, 9900/μL; aspartate aminotransferase, 49 IU/L; alanine aminotransferase, 22 IU/L; lactate dehydrogenase, 359 IU/L; ALP, 3697 IU/L; glucose, 94 mg/dL; calcium, 10.0 mg/dL; phosphorus, 5.3 mg/dL; ferritin, 5.8 ng/mL; neuron-specific enolase, 23 ng/mL; EBV-specific antibody testing including viral capsid antigen (VCA)-IgG and -IgM, and EBV nuclear antigen (EBNA), were all negative. Serum ALP isoenzymes measured on agarose electrophoresis (Bio Medical Laboratories, Tokyo, Japan) had a slightly diffuse pattern with bimodal peaks between Fig. 1 Serum alkaline phosphatase (ALP) isoenzyme patterns in children with hyperphosphatasemia. (a) Present case: bimodal peaks between ALP 2 and 3 indicate benign transient hyperphosphatasemia. (b) Fourteen-month-old boy with serum ALP = 1319 IU/L: a single peak between 2 and 3 indicates normal bone growth in a healthy infant. (c) Seven-year-old girl with serum ALP = 1007 IU/L and Epstein-Barr virus infection: liver dysfunction with cholestasis. Serum ALP isoenzymes were measured on agarose electrophoresis (Bio Medical