In June 2020, a 64 year old male was referred to the Infectious Diseases Day Ward at the Queen Elizabeth Hospital Hong Kong, for 3-month history of intermittent milky urine and weight loss of 6 kg. He had history of Kallmann syndrome (idiopathic hypogonadotropic hypogonadism), diabetes mellitus, hypertension and hyperlipidemia. There was no associated fever, night sweat, hematuria, loin pain or chest symptoms. He had no history of tuberculosis infection, or surgery / instrumentation to the urinary tract, and had no history of travel or residence in filaria-endemic countries. Other than general muscle wasting, there were no palpable lymph node or abnormal skin lesion on physical examination.
Urine collected was milky in appearance (Fig. 1) and was tested positive for chyle. Bacterial culture was negative while cytological examination showed lymphocyturia. Blood smears were negative for microfilariae. Four early morning urine specimens collected over a three-week period were negative on Ziehl-Neelson stain, but all yielded positive growth of acid-fast bacilli (AFB) after one to two weeks of incubation. MPB64 antigen test (a lateral flow immunochromatographic assay that detects the Mycobacterium tuberculosis complex-specific antigen MPB64) was negative. All isolates were subsequently confirmed to be Mycobacterium fortuitum, which was susceptible to amikacin, imipenem, ciprofloxacin, trimethoprim-sulfamethoxazole (SXT), doxycycline and linezolid, intermediately resistant to cefoxitin and resistant to clarithromycin. Blood specimen was negative for AFB culture, while chest X-ray did not show any infiltration to suggest active infection. Lymphopenia of 0.4 - 1.1 x 10^3 cells/uL was noted while renal function test and C-reactive protein were normal. Anti-HIV antibody was negative. PET-CT scan of whole body showed the absence of structural abnormality of the urinary tract, abnormal mass, lymphadenopathy or focal FDG uptake.
Once the susceptibility test result was available, treatment was started using intravenous amikacin 10 mg/kg daily, oral SXT 960 mg twice per day and oral levofloxacin 500 mg daily. After 2 weeks of three-drug treatment, regimen was switched to two-drug treatment with levofloxacin 500 mg daily and doxycycline 100 mg twice per day for another 24 weeks. SXT was substituted due to suspected drug-related hyponatremia. Medium chain triglyceride diet was also advised. In view of lymphopenia, CD4/CD8 subsets were checked which were low at 78 and 75 cells/uL respectively. Anti-interferon-gamma antibody was tested negative.
During the 6-month course of antimicrobial treatment till mid-December 2020, chyluria resolved clinically and multiple urine cultures collected after day 12 of treatment were negative for AFB. Four months after treatment completion, there was no recurrence of chyluria clinically, and urine cultures for AFB were repeatedly negative.