Laboratory Studies
The diagnosis of congenital self-healing reticulohistiocytosis depends on the presence of the histopathologic features of the disease and either CD-1a–positive staining of cells or the finding of Birbeck granules using electron microscopy.
A skin biopsy is required for the diagnosis; a punch biopsy is preferable. Laboratory studies should include a CBC count, serum chemistries, liver function tests, coagulation studies, and urine osmolarity. [38] Depending on the clinical presentation, other studies to consider would include the following:
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Gram stain
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Skin scrapings for scabies
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Potassium hydroxide and Tzanck preparations
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Bacterial, viral, and fungal cultures
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TORCH (toxoplasmosis, other infections, rubella, cytomegalovirus infection, and herpes) serologies
Imaging Studies
The following imaging studies may be warranted:
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Abdominal ultrasound
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Chest, skull, and long bone radiographs
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MRIs of the chest and abdomen
Other Tests
Bone marrow aspiration may be needed.
Histologic Findings
The histologic findings are often indistinguishable from Langerhans cell histiocytosis (LCH). Hematoxylin and eosin–stained sections demonstrate a polymorphous infiltrate of histiocytes, mononuclear cells, neutrophils, eosinophils, and mast cells involving the papillary and reticular dermis (see image files below). [39] Extension of the infiltrate to the fat is rare. Crusting and epidermal ulceration are common. Infiltrating Langerhans cells often exhibit indented or kidney-shaped nuclei (see image files below). Epidermotropism and the formation of intraepidermal microabscesses of Langerhans cells may be seen (see image below). Usually, Langerhans cell histiocytes have a scant amount of cytoplasm, but, on occasion, large mononuclear or multinucleated histiocytes may have abundant eosinophilic ground-glass cytoplasm that may mimic the giant cells of reticulohistiocytosis. An increased number of mast cells may be noted.
Hematoxylin and eosin–stained section (400X) showing hemorrhage and infiltration of papillary dermis and epidermis with mononuclear and histiocytic (Langerhans) cells with reniform nuclei.
Hematoxylin and eosin–stained section (400X) showing an intraepidermal collection of histiocytic (Langerhans) cells with prominent reniform nuclei.
The histologic diagnosis should be confirmed with immunohistochemical stains. Langerhans cells stain positive for CD-1a (see image below) and S-100. Other stains available are peanut agglutinin (PNA), placental alkaline phosphatase (PLAP), and interferon-gamma receptor. These stains are not specific for congenital self-healing reticulohistiocytosis; they stain all forms of LCH.
Immunohistochemical staining with CD-1a shows positive staining of cells within intraepidermal microabscesses.
No significant differences in the expression of E-cadherin, PHH3, and Ki-67 have been found in comparisons of cases of congenital self-healing reticulohistiocytosis and disseminated LCH. [15]
Langerhans cells also demonstrate the presence of Birbeck (tennis racket) granules on electron microscopy (see image below). CD207 or Langerin is a new immunostain that can also identify Birbeck granules. [38]
Some differences have been noted ultrastructurally between congenital self-healing reticulohistiocytosis and systemic forms of LCH. Electron microscopy reveals approximately 50% of cells in LCH have Birbeck granules, compared with only 10-30% of congenital self-healing reticulohistiocytosis cells. Transformation of Birbeck granules to laminated dense bodies is noted in congenital self-healing reticulohistiocytosis and may reflect degenerative changes. Some authors regard the coexistence of laminated dense bodies and Birbeck granules as indicative of congenital self-healing reticulohistiocytosis. [40]
Currently, however, no histologic or laboratory means is available to distinguish congenital self-healing reticulohistiocytosis from LCH. Spontaneous regression of the lesions and lack of systemic disease are the only means to differentiate these disorders.
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Urticarial patches on the leg of a 3-month-old infant and several reddish-brown papules on the foot typical of congenital self-healing reticulohistiocytosis.
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Reddish-brown papules of congenital self-healing reticulohistiocytosis on the foot of a 3-month-old infant.
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Hematoxylin and eosin–stained section (400X) showing hemorrhage and infiltration of papillary dermis and epidermis with mononuclear and histiocytic (Langerhans) cells with reniform nuclei.
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Hematoxylin and eosin–stained section (400X) showing an intraepidermal collection of histiocytic (Langerhans) cells with prominent reniform nuclei.
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Immunohistochemical staining with CD-1a shows positive staining of cells within intraepidermal microabscesses.
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Electron microscopy demonstrating cytoplasmic Birbeck (tennis racket) granules.
