Objective:

The impact of tuberculosis (TB) on mortality and morbidity is indisputable worldwide and even more so in countries with a high prevalence of Human Immunodeficiency Virus (HIV) co-infection. The development of a non-invasive diagnostic tool that is capable of early and accurate detection, staging and follow-up evaluation of tuberculosis is crucial in minimizing its devastating effects. We evaluated PET/CT imaging with a novel tracer, 68Ga-citrate,in this setting.

Rubinstein-Taybi syndrome (RSTS), a genetic disorder characterized by growth retardation, mental deficiency, dysmorphic face, broad thumbs and large toes, generally affects monozygotic twins concordantly. Thyroid hypoplasia (TH) is a common cause of congenital hypothyroidism (CH) and often accompanies dysmorphic syndromes. A pair of female twins were admitted to our neonatology unit 16 hours after delivery. They were born at 35 weeks of gestation. Both twins had an unusual dysmorphic facial appearance with microcephaly, as well as broad short thumbs and large toes. Based on the presence of characteristic dysmorphic features, the twins were diagnosed as RSTS. Thyroid function tests in the first twin revealed the following results: free thyroxine (T4) 8.4 pg/mL, thyrotropin (TSH) 4.62 mIU/L, thyroglobulin (TG) 213.24 ng/mL and a normal level of urinary iodine excretion (UIE). Thyroid function test results in the second twin in the second week were: free T4 5.9 pg/mL, TSH 9.02 mIU/L, TG 204.87 ng/mL, and normal UIE levels. Thyroid volumes were 0.36 mL and 0.31 mL in the first and second twin, respectively. TH was confirmed by technetium 99 m pertechnetate thyroid scans in both infants. Thyroid function tests normalized with L-thyroxine replacement therapy (10 µg/kg/day) around the end of the 3[sup]rd[/sup] week of life. The infants were discharged planning their follow-up by both endocrinology and cardiology units. The rarity of cases of twins with RSTS (concordant) co-existing with CH led us to present this report.

Results:

All 13 patients demonstrated abnormal tracer accumulation in the lungs or extra-pulmonary or both. 68Ga-citrate accumulated in every lung lesion noted on CT in six cases (46%). In seven cases (54%) some of the lung lesions noted on CT were not 68Ga-citrate avid, which is suggestive of non-active tuberculosis lesions. Ten patients (77%) demonstrated extra-pulmonary involvement, which included various lymph node groups, skeletal lesions, pleural-, splenic- and gastro-intestinal tract involvement. More extra-pulmonary lesions were detected on PET compared to CT in eight cases (80%). The results of dual-time point imaging varied significantly amongst study participants.

Conclusion:

Pulmonary and extra-pulmonary tuberculosis lesions demonstrate 68Ga-citrate accumulation; with more extra-pulmonary lesions detected on PET compared to CT. 68Ga-citrate PET may also provide a way of distinguishing active from inactive lesions for treatment response evaluation.

Keywords: 68Gallium-citrate,PET/CT,tuberculosis