Chronic mucocutaneous candidiasis (CMC) is characterized by increased susceptibility to skin, mucosa, and nail infections caused by Candida species and dermatophytes. CMC is found in patients with various acquired or inherited immune disorders (1, 2). The autosomal dominant (AD) signal transducer and activator of transcription protein (STAT) 1 gain of function (STAT1 GOF) is the most frequent genetic cause of CMC (3, 4). STATs are critical signaling molecules downstream of interferons (IFNs), cytokines, growth factors, and hormones, which upon binding to their receptors lead to the activation of Janus kinases, which recruit and phosphorylate cytoplasmic STAT proteins (JAK–STAT signaling pathway). Phosphorylated STATs form homo- or heterodimers and translocate to the nucleus where they bind to specific promoters to initiate transcription (5). Most of the STAT1 GOF variants are located in the coiled-coil and DNA-binding domains of STAT1 (6). These variants result in enhanced STAT1 phosphorylation, as compared to wild-type STAT1, due to impaired nuclear dephosphorylation (4), and enhanced STAT1 signaling downstream of STAT1-dependant cytokines, such as IFN-α/β, IFN-γ, and interleukin (IL)-27, as well as downstream STAT3-dependent cytokines, such as IL-6 and IL-21, resulting in impaired Th17 cell development (4, 7). Patients with STAT1 GOF present heterogeneous symptoms; CMC is present in nearly all cases often associated with other infectious (bacterial, fungal, or viral) and noninfectious (autoimmunity/inflammatory, aneurysm, and tumor) clinical features (6, 8). Rosacea-like demodicosis is an emerging manifestation reported among the patients with STAT1 GOF, with only a few cases recently described in the literature (9–14), related to Demodex proliferation. We report the case of a patient with a novel heterozygous STAT1 mutation, shown by functional study to be GOF, who presented CMC associated with recurrent pneumonia and florid rosacea-like demodicosis affecting the center of the face and the eyelids.

A 40-year-old woman has been hospitalized in our department of infectious diseases in February 2018 for fever and cough. Her medical history included CMC since 7 years of age which had never been explored, and esophageal candidiasis in 2015 showing recurrence despite treatment with fluconazole. She had a 3-year-old healthy boy, and no other case was reported in her family.

Upon admission, the patient was diagnosed with pneumonia associated with bronchiectasis via clinical and radiological examinations. Microbiological examination revealed Streptococcus pneumoniae in the sputum. On clinical exam, marked oral candidiasis and diffuse inflammatory papules on the face associated with bilateral blepharitis were noted ( Figure 1 ). The patient was successfully treated with ceftriaxone but experienced another episode of pneumonia in June 2018, which resolved after further treatment with ceftriaxone. The patient denied receiving any treatment for CMC.

A direct examination of the eyelashes revealed the presence of Demodex folliculorum ( Supplementary Material , Appendix 2 ). Skin biopsy also revealed non-granulomatous peripilar inflammation with the presence of numerous Demodex within the follicles ( Figure 2 ). A diagnosis of florid rosacea-like demodicosis was therefore established. Treatment with oral doxycycline (100 mg/day) led to the partial improvement of the lesions. Similarly, oral ivermectin (200 µg/kg, thrice a week) in combination with a daily topical application of ivermectin led to the partial improvement of the lesions. Finally, lasting remission was achieved with the resumption of doxycycline in combination with the local application of 1.5% metronidazole.

Inherited CMC has been reported in many inborn errors of immunity impairing the IL-17A/F axis (2, 7). Up to now, the genetic defect responsible for most of the reported cases of CMC is autosomal dominant STAT1 GOF, described in 2011, with various heterozygous mutations located in the coiled-coil domain of STAT1 associated with exaggerated IFN-α/β and IFN-γ responses and low Th17 cell proportions (3, 4, 7). As many as 105 mutations at 72 amino acid residues, including 65 recurrent mutations, have already been reported in more than 400 patients worldwide (7). STAT1 GOF can lead to a wide variety of clinical manifestations, with CMC being nearly constantly observed (3, 4, 6, 8). However, rosacea was not reported in the first descriptions of STAT1 GOF in 2011 (3, 4). A cohort of 26 patients with STAT1 GOF reported skin infections, such as pustules, furunculosis, or folliculitis, but not rosacea (6). However, some cases of demodicosis can manifest with folliculitis (16). In 2016, a large international cohort of 274 patients with STAT1 GOF from 167 kindreds originating across 40 countries was described (8). CMC was found in almost all patients (98%); however, the patients displayed a much broader and heterogeneous clinical phenotype, including other skin and invasive infectious diseases, autoimmune diseases (37%), cerebral aneurysm (6%), and/or cancers (6%) (8). Our patient presented CMC, pneumonia, and bronchiectasis, as well as florid rosacea, a clinical form not reported in the two series, but only in 20 other cases among 6 different families ( Table 1 ) (9–14). The pathophysiology causing rosacea in STAT1 GOF remains unknown. However, it is suspected that the immunodeficiency related to STAT1 GOF facilitates Demodex mite and bacterial proliferation involved in rosacea affecting the face and, even more frequently, the eyelids. There is a link between Demodex and rosacea (17) explaining the success of ivermectin treatment in some patients with STAT1 GOF (9, 10). We did not perform a density count for Demodex, but the Demodex load appeared high and the presence of Demodex infection was easily confirmed. However, the antiparasitic treatment was not effective, and it is only in combination with more conventional rosacea therapies that the treatment ultimately achieved the patient’s lasting remission. Other microbes, especially bacteria such as Bacillus oleronius, whether they are harbored or not by Demodex are involved in the pathophysiology of rosacea. This finding may explain the success of the patient’s treatment with tetracyclines (18). Rosacea is a chronic inflammatory skin disease affecting typically the convexities of the face, with the possibility of ocular involvement (subtype 4) (19). A retrospective study of 115 cases of demodicosis reported three cases related to immunodeficiencies (20). Demodicosis in patients with human immunodeficiency virus infection (21–24), with an immune reconstitution inflammatory syndrome (25–28), or in a patient with ataxia-telangiectasia (29) has been reported. The impaired IL-17-mediated immunity, with low Th17 cell proportions, in STAT1 GOF patients may explain the proliferation of Demodex (30), leading to the occurrence of demodicosis, especially rosacea-like demodicosis (31). Rosacea-like demodicosis could also be more prevalent but under-recognized in those with inborn errors of immunity.

In conclusion, we describe a patient heterozygous for a novel STAT1 GOF mutation. The phenotype includes CMC, bacterial pneumonia, and florid rosacea-like demodicosis with ocular involvement. Rosacea-like demodicosis appears as an increasingly recognized clinical feature among individuals with STAT1 GOF mutations. Therefore, a thorough cutaneous examination of patients with STAT1 GOF should carefully evaluate the presence of rosacea-like demodicosis, which can be easily omitted in clinical practice, and rosacea related to chronic demodicosis should be considered among symptoms suggestive of STAT1 GOF.

The datasets presented in this article are not readily available because the consent obtained did not include making this publicly available. However, the variant data can be found at https://www.ncbi.nlm.nih.gov/clinvar/ under the accession number SCV001885896. Requests to access the datasets should be directed to the corresponding author.

Written informed consent was obtained from the individual for the publication of any potentially identifiable images or data included in this article.

MM, AK, and AG conceived and designed the case report, contributed to the clinical and pathology diagnosis, collected all data, and wrote the manuscript. AP, AK, MM, LS, SO and JT contributed to the pathology diagnosis, immunohistochemistry, and its photographic material. EB, JS, AM, and LD contributed to the dermatologic evaluation and skin biopsies. All authors critically revised the manuscript for important intellectual content, provided approval of the final version, and agreed to be accountable for all aspects of the work. All authors contributed to the article and approved the submitted version.

The work was funded by the French National Research Agency (ANR) under the “Investments for the future” program (ANR-10-IAHU-01), the ANR-18-CE93-0008-01, the Integrative Biology of Emerging Infectious Diseases Laboratory of Excellence (ANR-10-LABX-62-IBEID), and the National Institute of Allergy and Infectious Diseases of the NIH (grant no. R01AI127564). This study was supported by the European Reference Networks for Rare Diseases (ERN) Rare Immunodeficiency, Autoinflammatory, and Autoimmune Diseases (RITA).

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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