A 3 3/12-year-old boy was admitted to Tomo Hospital with remittent fever on March 16, 1973.In June, 1972 he suffered from measles and a few weeks later an abscess with a dischargingsinus developed at his left axillar groove, successively spreading to another regions such asparotid and submandibular areas. The chest roentgenogram taken four months later exhibitedlung infiltrations and the biopsy of left axillar lymphnode aroused the suspicion of reticulohistiocytosis histologically (Fig.9). In his past history, he tolerated to variola and polio vaccinesand showed negative to Montoux reaction when he was one year old, but it is uncertainwhether he received BCG inoculation or not.<BR>On admission, the boy had several abscesses with discharging sinuses at axillar, preauricular, parotid, submandibular and tibial regions and was in ill condition. X-ray revealed several lyticlesions of the skull and extremity bones (Fig.1&2) and pulmonary infiltrations (Fig.3&4).The acid-fast bacilli isolated from pus, sputum and gastric juice, were indistinguishable fromBCG by bacteriological investigations (Table 1). The biopsy specimens from cervical and tibialsinuses and a lymphnode revealed an inflammatory granulomatous tissue infiltrated chiefly byhistiocytes and lacked epithelioid tubercle, giant cell and caseation (Fig. 10). By Ziel-Neelsen'sstain, numerous acid-fast bacilli were detected in the cytoplasma of histiocytes (Fig.11) and thegreenish staining by Murohashi's differential staining with marachite-green and fuchsin suggestedthat they were living organisms.<BR>While he was treated with kanamycin, isoniazid, rifampicin and ethambutol, the remittentfever subsided gradually but his deteriorated condition persisted till 3 months later when hereceived the transfusion of 200 ml of blood. Thereafter his condition became better gradually.The acid-fast bacilli were not detected on culture in May, 1973, but positive on smear untilDecember, 1973 (Fig.5). At his discharge on September 15, 1974, X-ray film revealed a markedregression of bony and pulmonary lesions (Fig.6, 7&8).<BR>In immunological examination, serum irnmunoglobulins were within the normal range. Thedelayed skin reaction against DNCB and PPD or SK-SD which were negative on admissionconverted to positive nine months and 1 5/12 years later, respectively. The decreased percentageof E-rosette forming cells (T-cells) examined in May, 1973 restored to normal range in August, 1973 and September, 1974. 3H-thymidine incorporation into lymphocytes in April, 1974 whenhis condition had ameliorated, revealed normal with PHA and SK-SD, but slightly decreasedwith PPD (Table 2).