Alcaptonuria: a case complicated with valvular heart disease and immunodeficiency.

A 75-year-old man was diagnosed with alcaptonuria by direct identification of homogentisic acid in the urine using gas chromatography-mass spectrometry. Complications included valvular heart disease with marked calcification detected by two-dimensional color-Doppler echocardiography and recurrent bacterial infection. Immunological analyses revealed a reduced number of T cells with compensatory expansion of CD56+, CD57+ natural killer (NK) cell population and impaired functions of cellular immunity such as phytohemagglutinin response, antibody-dependent cellular cytotoxicity, NK activity and interleukin-2 production. Humoral immunity and neutrophil functions were considered to be normal. This is the first reported case of alcaptonuria to our knowledge in which immunological abnormality was documented.