WBR0326
| Author | [[PageAuthor::Rim Halaby, M.D. [1], Alison Leibowitz [2] (Reviewed by Alison Leibowitz)]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Pathology |
| Sub Category | SubCategory::Hematology |
| Prompt | [[Prompt::A 13-year-old female presents to the physician's office for excessive thirst, frequent urination, and weight loss. She reports raised scalp lesions that are increasing in number. Upon physical examination, you observe skull lesions, cervical lymphadenopathy, and exophthalmus. A CT scan displays osteolytic coalescent lesions of the skull with a "georgraphical skull" appearance. A biopsy of the skin lesions demonstrates dermal infiltration of clustering cells, with large ovoid pink cytoplasm under light microscopy. Immunofluorescence exhibits positive staining for S100 and CD1a and electron microscopy reveals the presence of pentalaminar membranous organelles, resembling tennis rackets, near the nuclear membrane. Which of the following diagnoses most likely corresponds with the findings?]] |
| Answer A | AnswerA::Langerhans cell histiocytosis |
| Answer A Explanation | AnswerAExp::See Explanation |
| Answer B | AnswerB::Schwannoma |
| Answer B Explanation | [[AnswerBExp::Schwannoma may exhibit positive S100 staining, but the other findings are not usually observed in schwannoma.]] |
| Answer C | AnswerC::Diabetes insipidus |
| Answer C Explanation | [[AnswerCExp::Although often diabetes insipidus can be associated with the Langerhans cell histiocytosis syndrome, it is not the isolated diagnosis in this scenario.]] |
| Answer D | AnswerD::Mastocytosis |
| Answer D Explanation | [[AnswerDExp::Mastocytosis can be associated with the Langerhans cell histiocytosis, it is not the isolated diagnosis in this scenario.]] |
| Answer E | AnswerE::Wiskott-Aldrich syndrome |
| Answer E Explanation | [[AnswerEExp::Patients with Wiskott-Aldrich syndrome (WAS) often have thrombocytopenic purpura, eczematous skin lesions, and recurrent infections, all of which may be present in Langerhans cell histiocytosis. Although WAS may be in the differential diagnosis of Langerhans cell histiocytosis, WAS does not account for all of the patient's clinical findings.]] |
| Right Answer | RightAnswer::A |
| Explanation | [[Explanation::Langerhans cell histiocytosis is a cancer-like heterongeous group of diseases characterized by the presence of epidermal dendritic cells called Langerhans cells. These cells are often called "nerve cells of the skin." Langerhans cell histiocytosis was once termed histiocytosis X due to the unclear etiology of the disease.
Hand-Schuller-Christian disease (HSC), eosinophilic granuloma, and Letterer-Siwe disease are all subgroups of Langerhans cell histiocytosis. The patient in this scenario has the classical clinical presentation of HSC disease, characterized by the triad of: diabetes insipidus, exophthalmus, and lytic bony lesions. Other systemic signs and symptoms may be present, such as lymphadenopathy, pulmonary findings, and hepatosplenomegaly. Often, light microscopy displays characteristic Langerhans cells, with large ovoid pink cytoplasm that diffusely infiltrate the dermal layer, resembling a granuloma, which exhibit the characteristic staining of Cla and S100 upon immunofluoresence. Electron microscopy demonstrates the characteristic tennis racket shaped Birbeck granules. Birbeck granules are pentalaminar membranous organelles located near the nuclear membrane. Treatment may include steroids or ultraviolet phototherapy for skin lesions, bisphosphonates for bone lesions, and chemotherapy for systemic involvement. |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::Langerhans, WBRKeyword::cell, WBRKeyword::histiocytosis X, WBRKeyword::langerhan, WBRKeyword::birbeck, WBRKeyword::granule, WBRKeyword::granules, WBRKeyword::S100, WBRKeyword::C1a, WBRKeyword::dendritic, WBRKeyword::dendrite, WBRKeyword::skull, WBRKeyword::lesion, WBRKeyword::osteolytic, WBRKeyword::diabetes, WBRKeyword::insipidus, WBRKeyword::exophthalmus |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |