Idiopathic CD4+ T-lymphocytopenia in a boy with Down syndrome. Report of a patient and a review of the literature.

Abstract

Idiopathic CD4+ T-lymphocytopenia (ICL) has been supposed to be a rare syndrome characterised by a decreased number of CD4+ T-lymphocytes (<300 CD4+ cells/ll or a CD4+ count <20% of total T cells) on two occasions and clinically manifested by opportunistic infections [11]. Also, any defined immunodeficiency disorder must be excluded such as human immunodeficiency virus (HIV), Epstein-Bar virus, and cytomegalovirus infection. We report on a boy with Down syndrome who was found to have ICL. A 6-year-old boy with Down syndrome was admitted because of an induration of subcutaneous tissue in the left lower abdominal wall. At 5 years and 1 month of age, a suture granuloma was excised which was caused by a silk string left after orchiectomy performed 3 years before for epididymitis. Ten months later a mass developed in the same region. Although he responded temporarily to oral antibiotics, the mass reappeared. Blood culture grew Stenotrophomonas maltophilia. On admission, the leukocyte count was 4,400/ll with 55.5% lymphocytes. C-reactive protein was negative, but the erythrocyte sedimentation rate was 54 mm/1 h. IgG antibody to Epstein-Bar virus capsid antigen was present in a titre of 1:40. Serum cytomegalovirus antibody was negative. Serum HIV-1 and HIV-2 antibodies were negative. Flow cytometric analysis showed the following: CD3+ T-lymphocyte counts (/ll) (% of total lymphocyte count), CD19, CD4, and CD8 were 1,709 (70.0%), 168 (6.9%), 530 (21.7%), and 1,424 (58.3%), respectively. Debridement was performed and the wound was left open after intravenous ceftazidime treatment. The postoperative course was uneventful. The CD4+ T-lymphocyte counts were persistently low for 1 year and 4 months and were less than 20% of total lymphocytes on four occasions (18.8%, 16.7%, 18.6%, and 19.7% at the age of 6 years and 4 months, 6 months, 8 months, and 10 months, respectively). Slightly reduced CD45RA expression (53.1%), slightly enhanced CD45RO expression (28.7%), and distinctly enhanced CD95 expression (71.0%) on CD4+ T cells were seen, compared to a control patient (70.6%, 15.9%, and 32.1%, respectively). Two patients were noted to have ICL among 22 patients with Down syndrome (male/female: 12/10, age 5 months to 31 years). One was a 25-year-old woman whose minimum CD4+ T-lymphocyte count was 278/ ll. The other was a 12-year-old, whose last two lymphocyte counts were 178 and 185/ll, respectively. Most patients reported with ICL are adults, but so far 28 children with ICL including our patient have been reported. The features of 18 symptomatic children with ICL are shown in Table 1. These children with ICL are thought to be at risk of developing opportunistic infections, but can be asymptomatic [7]. Stenotrophomonas maltophilia is a short to mediumsized straight gram-negative bacillus, which is isolated especially from immunocompromised hosts [9]. In the patient described here, the persistent tumour associated with Stenotrophomonas maltophilia infection prompted the immunological evaluation. Patients with Down syndrome are known to have immunological abnormalities including decreased numbers of CD4+ T-lymphocytes [5], but the extent of CD4+ T-lymphocytopenia is milder than that observed in ICL [1]. Genetic factors may cause ICL [2, 6], and the identification of trisomy 21 as a cause of ICL may aid in the identification of these genes.