Sibling cases of Mycobacterium avium complex disease associated with hematological disease

A 22-year-old man who was admitted to our respiratory division complaining of fever and cough of 1 month's duration had been diagnosed with myelodysplastic syndrome 5 years earlier. On admission, radiological findings showed bilateral diffuse small nodular shadows. Although the results of an acid-fast bacilli examination of blood, sputum, and urine samples were all negative, we initiated antituberculous therapy for suspected miliary tuberculosis because the histological diagnosis from a bone marrow biopsy was epitheloid granuloma. The abnormalities on his chest radiographs improved, but his left cervical lymph nodes became swollen. The histological result of a lymph node biopsy revealed epitheloid granuloma with caseating necrosis. The DNA-DNA hybridization result of a resected lymph node culture indicated Mycobacterium avium. The final diagnosis was disseminated Mycobacterium avium complex (MAC) disease. Both leukocytopenia and thrombocytopenia had been noted in the patient's 19-year-old younger brother, who had been living in the same home 5 years earlier, and for whom a diagnosis of myelodysplastic syndrome was made from bone marrow aspiration on admission. An infiltration shadow with nodular shadows was noted in the right upper lung field on a chest radiograph. A bronchoscopic examination revealed pulmonary MAC disease. As for the route of infection, although we investigated restriction fragment length polymorphism (RFLP), a different pattern was found in the two brothers. We suspect that they were infected by different species of Mycobacterium avium in the same environment rather than by droplet infection from the younger brother to the older brother.