RESUMO
BACKGROUND: Tuberculosis is the leading infectious cause of death worldwide. Among native Swiss people, tuberculosis is more common in older people than in younger people. Approximately 25-30% of reported cases of tuberculosis are purely extrapulmonary; skeletal tuberculosis is reported in 3-5% of cases. The purpose of this case report is to draw attention to the diagnostic challenge of tuberculous sacroiliitis with secondary psoas abscess, as this clinical picture is very rare. CASE PRESENTATION: A magnetic resonance imaging scan of an 85-year-old (Swiss-German) Caucasian woman with chronic left-sided hip pain and limitation of hip joint movement showed a progressive destruction of her sacroiliac joint and a large collection in her left iliopsoas muscle. Drainage of the abscess revealed pus; a polymerase chain reaction assay was positive for Mycobacterium tuberculosis complex. Tuberculous sacroiliitis with secondary iliopsoas abscess was diagnosed 9 months after the start of the symptoms. Combination treatment with isoniazid, rifampicin, pyrazinamide, and ethambutol was started. CONCLUSIONS: Sacroiliitis with secondary psoas abscess is an unusual cause of hip pain and is likely to be overlooked since joint pain of the lower extremity and lumbar pain are some of the most common complaints in older individuals. A high level of suspicion and invasive diagnostic procedures are needed for timely diagnosis of tuberculous sacroiliitis not only in immunocompromised patients living in or originating from endemic areas.