Langerhans cell histiocytosis presenting as a blueberry muffin rash

BRAF Mutation Analysis in Two Cases of Congenital Self-Healing Langerhans Cell Histiocytosis

Congenital self-healing Langerhans cell histiocytosis (CSHLCH) is a rare type of Langerhans cell histiocytosis (LCH). Here, we report two cases of CSHLCH. The cases presented solitary and multiple skin lesions of various sizes. The diagnosis was confirmed by skin biopsies. The lesions disappeared after one to two months without therapeutic intervention. No BRAF mutations in the skin lesions were detected, and soluble interleukin-2 receptor (sIL-2R) was normal in both cases. Recent studies suggested that the state of differentiation of the precursor cell in which BRAF mutations occur is associated with the clinical types and prognosis of the disease. Further investigation should be needed to elucidate the association between the progression and regression of CSHLCH and BRAF mutation.

Case report: "Congenital cutaneous langerhans cell histiocytosis presenting with blueberry Muffin Rash"

Congenital cutaneous Langerhans cell histiocytosis-(LCH), named Hashimoto Pritzker disease, is a rare subtype among the clinical spectrum of LCH that often presents at birth or through the neonatal term and spontaneously resolve within a few months. In rare instances, infants with congenital cutaneous LCH may present with a blueberry-muffin rash. We reported a case of a male newborn who presented with blueberry muffin rash and was diagnosed with congenital cutaneous LCH later on. The diagnosis was confirmed by excluding other possible systemic causes of blueberry muffin rash, followed by a skin biopsy. Skin biopsy showed reticular dermis-hypodermis infiltration by medium-sized cells which had a pale eosinophilic cytoplasm and irregular nuclei. The lesional cells were positive for Langerin, CD1a, S100, and CD68 immunostains, consistent with congenital cutaneous LCH. Investigations were performed and revealed no systematic disease involvement. After a discussion with the pediatric Hemato-Oncologist, the decision was to keep track of a "wait-and-see" approach. Long-term follow-up revealed no recurrence of the cutaneous lesions or any systemic involvement, which further leads to congenital cutaneous LCH diagnosis. Even though it is very rare, blueberry muffin rash differential diagnosis should include congenital cutaneous LCH. Early recognition of this condition protects patients from unnecessary and possibly unsafe systemic treatment.

A Case Report of Pediatric Langerhans Cell Histiocytosis: Current Approach and Diagnostic Challenges for Dermatologist

Langerhans Cell Histiocytosis (LCH) is a chronic and rare myeloproliferative disorder caused by disorders in Lang-erhans cell proliferation in various organs and tissues. LCH has a wide variety of clinical manifestations, making it difficult to diagnose. Cutaneous manifestations are polymorphic in the form of purpura, papule, vesicles and pustules. LCH can involve vital organs such as the liver and lungs as well as the hematopoiesis system that usually gives a poor prognosis. The prognosis is also influenced by the age of patient, organ dysfunction and response to the first 6 weeks of chemotherapy treatment. A 3-year-old girl reported a major complaint of an abscess-like lesion in the region of neck accompanied by an extensive purpura of scalp, neck and inguinal areas accompanied by vulvar erosions. The immunohistochemical and histopathologic examination support LCH and the clinical improvement after intravenous administration of intravenous 3 mg/m2 Vinblastine chemotherapy, 75 mg/m2 etoposide, oral 40 mg/m2 per prednisone. After the 6th cycle of chemotherapy, the patient died.

Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is caused by clonal expansion of myeloid precursors that differentiate into CD1a+/CD207+ cells in lesions that leads to a spectrum of organ involvement and dysfunction. The pathogenic cells are defined by constitutive activation of the MAPK signaling pathway. Treatment of LCH is risk-adapted: patients with single lesions may respond well to local treatment, whereas patients with multisystem disease require systemic therapy. Although survival rates for patients without organ dysfunction is excellent, mortality rates for patients with organ dysfunction may reach 20%. Despite progress made in the treatment of LCH, disease reactivation rates remain above 30%, and standard second-line treatment is yet to be established. Treatment failure is associated with increased risks for death and long-term morbidity, including LCH-associated neurodegeneration. Early case series report promising clinical responses in patients with relapsed and refractory LCH treated with BRAF or MEK inhibitors, although potential for this strategy to achieve cure remains uncertain.

A mutation in POLR3E impairs antiviral immune response and RNA polymerase III

RNA polymerase (Pol) III has a noncanonical role of viral DNA sensing in the innate immune system. This polymerase transcribes viral genomes to produce RNAs that lead to induction of type I interferons (IFNs). However, the genetic and functional links of Pol III to innate immunity in humans remain largely unknown. Here, we describe a rare homozygous mutation (D40H) in the POLR3E gene, coding for a protein subunit of Pol III, in a child with recurrent and systemic viral infections and Langerhans cell histiocytosis. Fibroblasts derived from the patient exhibit impaired induction of type I IFN and increased susceptibility to human cytomegalovirus (HCMV) infection. Cultured cell lines infected with HCMV show induction of POLR3E expression. However, induction is not restricted to DNA virus, as sindbis virus, an RNA virus, enhances the expression of this protein. Likewise, foreign nonviral DNA elevates the steady-state level of POLR3E and elicits promoter-dependent and -independent transcription by Pol III. Remarkably, the molecular mechanism underlying the D40H mutation of POLR3E involves the assembly of defective initiation complexes of Pol III. Our study links mutated POLR3E and Pol III to an innate immune deficiency state in humans.

Case of Congenital Self-Healing Reticulohistiocytosis Expanding the Spectrum of Blueberry Muffin Baby

Congenital self-healing reticulohistiocytosis (CSHRH) is a benign, rare variant of histiocytosis. This condition can present phenotypically as blueberry muffin baby. This is the case of a male neonate with skin involvement of papulonodular violaceous lesions, which resolved spontaneously. The diagnosis of CSHRH is confirmed using histopathology and immunohistochemistry.