A 6-year-old boy is brought to the office for evaluation of leg pain. The pain has been constant for the last 2 weeks and keeps the patient from playing with his friends. It is worse at night and has made it difficult for the child to fall asleep. He wakes up several times nightly to void and has had episodes of incontinence as the leg pain prevents him from walking to the bathroom. The patient has had no recent fever or dysuria. Temperature is 36.7 C (98 F). Cardiac examination reveals tachycardia; no murmurs are present. A soft, non-fluctuant, tender, 5-cm (2.5-in) mass over the right anterior distal thigh without overlying erythema is noted. The right knee has full range of motion, and no effusion is noted. An erythematous, papular rash is present over the chest, trunk, and groin. Laboratory results are as follows: Skeletal survey reveals a single small, well-defined, lytic distal femoral diaphyseal lesion. Which of the following is the most likely diagnosis in this patient?

Question

A 6-year-old boy is brought to the office for evaluation of leg pain.  The pain has been constant for the last 2 weeks and keeps the patient from playing with his friends.  It is worse at night and has made it difficult for the child to fall asleep.  He wakes up several times nightly to void and has had episodes of incontinence as the leg pain prevents him from walking to the bathroom.  The patient has had no recent fever or dysuria.  Temperature is 36.7 C (98 F).  Cardiac examination reveals tachycardia; no murmurs are present.  A soft, non-fluctuant, tender, 5-cm (2.5-in) mass over the right anterior distal thigh without overlying erythema is noted.  The right knee has full range of motion, and no effusion is noted.  An erythematous, papular rash is present over the chest, trunk, and groin.  Laboratory results are as follows:  Skeletal survey reveals a single small, well-defined, lytic distal femoral diaphyseal lesion.  Which of the following is the most likely diagnosis in this patient?

Quizplus · Accepted Answer

11ec25c8_d737_3903_bc81_1b4e25541275_MD0003_00 This child has a lytic bone lesion, rash, and signs of diabetes insipidus (ie, polyuria, hypernatremia) consistent with Langerhans cell histiocytosis (LCH). LCH is a rare disorder in which histiocytes (macrophages within tissue) proliferate and infiltrate one or more organ systems. Bone is most commonly affected, but invasion of the skin (eczematous rash), lymph nodes, lungs (cough, pulmonary nodules), liver, spleen, and CNS (central diabetes insipidus with polyuria and hypernatremia) can also occur. Bone lesions are frequently found in the skull; the femur, vertebrae, and other bones can also be affected. Lesions may be asymptomatic or associated with local pain and an overlying tender mass. X-ray shows characteristic "punched-out" lytic lesions; biopsy is required to confirm the diagnosis. X-ray Although the bone tumors are benign, they can be locally destructive and are typically treated with curettage or chemotherapy (eg, prednisone). (Choice B) Multiple myeloma is a plasma cell dyscrasia that presents with multiple osteolytic bone lesions. It is rarely found in children and a single lytic lesion is uncommon. (Choice C) Osteogenesis imperfecta presents with blue sclerae, diffuse cortical thinning, attenuation of trabeculae, and pathologic fractures. A solitary lytic bone lesion would not be expected. (Choice D) Osteoid osteoma is a benign bone tumor that typically presents in adolescents with bone pain that is worse at night and resolves with nonsteroidal anti-inflammatory medications. A small, round hypodensity is seen on x-ray. Osteoid osteoma is less likely in this child with concomitant rash and diabetes insipidus. x-ray (Choice E) Osteomyelitis generally presents acutely with bony tenderness, swelling, and fever. Although initial x-rays may be normal, later they may show cortical loss and new bone formation. This patient has no fever, and osteomyelitis is not associated with rash and hypernatremia. (Choice F) Osteosarcoma is the most common primary bone malignancy and presents with localized pain and swelling in long bone metaphyses. X-ray findings include periosteal elevation (Codman triangle) and a "sunburst" pattern of new bone formation, which are not seen on this patient's skeletal survey. metaphyses X-ray Educational objective: Langerhans cell histiocytosis frequently presents with lytic bone lesions and an eczematous rash. Additional presenting signs can include central diabetes insipidus, lymphadenopathy, hepatosplenomegaly, and cough. References: Diagnosis and management of Langerhans cell histiocytosis. (http://www.ncbi.nlm.nih.gov/pubmed/25281259) Clinical characteristics and treatment of Langerhans cell histiocytosis. (http://www.ncbi.nlm.nih.gov/pubmed/26461147)

A 6-Year-Old Boy Is Brought to the Office for Evaluation