Helper T cell immunity in humans with inherited CD4 deficiency.

CD4+ T cells are vital for host defense and immune regulation. However, the fundamental role of CD4 itself remains enigmatic. We report seven patients aged 5-61 years from five families of four ancestries with autosomal recessive CD4 deficiency and a range of infections, including recalcitrant warts and Whipple's disease. All patients are homozygous for rare deleterious CD4 variants impacting expression of the canonical CD4 isoform. A shorter expressed isoform that interacts with LCK, but not HLA class II, is affected by only one variant. All patients lack CD4+ T cells and have increased numbers of TCRαß+CD4-CD8- T cells, which phenotypically and transcriptionally resemble conventional Th cells. Finally, patient CD4-CD8- αß T cells exhibit intact responses to HLA class II-restricted antigens and promote B cell differentiation in vitro. Thus, compensatory development of Th cells enables patients with inherited CD4 deficiency to acquire effective cellular and humoral immunity against an unexpectedly large range of pathogens. Nevertheless, CD4 is indispensable for protective immunity against at least human papillomaviruses and Trophyrema whipplei.

Complicated Cutaneous Leishmaniasis in a Patient under Combined Immunosuppression.

Species associated with visceral leishmaniasis, such as L. infantum, may be responsible for cutaneous leishmaniasis (CL), particularly in the Mediterranean region. In immunosuppressed hosts, classification as complicated CL is essential, as the risk of mucosal leishmaniasis warrants systemic therapy. We report the case of a forty-seven-year-old male living in Portugal, with Fabry disease and receiving immunosuppressive treatment with adalimumab and methotrexate for Crohn's disease. There was no travel history outside of Europe. He presented a two-year-old, 5.5 cm plaque with a well-defined hyperkeratotic elevated border and central, painless ulceration on his back. The biopsy revealed parasites inside macrophages suggestive of Leishmania, and PCR identified the species as L. infantum. A biopsy via nasal endoscopy excluded mucosal involvement. Classification as complicated CL dictated treatment with liposomal amphotericin B and subsequent topical paramomycin. The rarity of CL in Portugal may delay its diagnosis, especially in autochthonous infections. Treatment choice is complicated by the heterogeneity of drugs available worldwide. As the global prevalence of CL increases, it is important to be aware of this diagnosis.

Painless rash in a transplant patient.

Dermatophytes are common keratinophilic fungi responsible for superficial skin infections. Deep dermatophytosis is a rare form of invasive skin infection described in immunocompromised patients. We report the case of a 65-year-old man with a history of an orthotopic liver transplant for hepatocarcinoma 6 months earlier, who presented with small painless erythematous papules in lower limbs, some of which were umbilicated. Skin biopsy showed an intense non-necrotizing granulomatous reaction in the dermis around fungal structures. Trichophyton rubrum was identified as the causal agent through culture and internal transcribed spacer sequencing.