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A 15-Month-Old Boy With Blue-Gray Macules

Educational Objective
Based on this clinical scenario and the accompanying image, understand how to arrive at a correct diagnosis.
1 Credit CME

A 15-month-old boy with congenital heart disease, seizures, and developmental delay was admitted to the hospital for a methicillin-resistant Staphylococcus aureus retropharyngeal abscess and methicillin-resistant Staphylococcus aureus bacteremia treated with vancomycin and clindamycin. The dermatology department was consulted for a diffuse truncal rash concerning for a drug rash given the initiation of several antibiotics during his hospital stay. On admission, he was noted to have several scattered 2-mm pink papules on his trunk and extremities and a high density of blue-gray macules on his trunk. The duration of his skin lesions was unknown. He was up-to-date on all of his immunizations. He lived with his parents, aunt, uncle, and 3-year-old cousin. His cousin received a diagnosis of chicken pox 6 months prior, but had persistent skin lesions and pruritus. His mother had several pruritic pink papules on her bilateral forearms, which she suspected were from sand fleas.

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B. Pediculosis corporis

The clinical appearance of blue-gray macules, or maculae ceruleae, is pathognomonic for lice infestation. On further questioning, the patient’s father revealed that he had recently received a diagnosis of body lice. The illness diagnosis in this patient was confirmed by his exposure history and the presence of pink papules representing lice bites in the center of the evolving maculae ceruleae.

The blue-gray pigment in maculae ceruleae is associated with extravasated erythrocytes and a lymphocytic infiltrate on histology.1 The etiology of this pigment is not well studied, but some think it is because of the conversion of bilirubin to biliverdin by the insect saliva,2 while others attribute it to hemosiderin deposition deep in the dermis.1,3 Maculae ceruleae is more apparent in thin, light-colored skin, such as in this patient.4 Body lice bites typically occur along the neck, axillae, and waist, where clothing fits the tightest.5 The 15-month-old patient typically wore a fitted onesie, and his bites occurred where the onesie snugly contacted his trunk.

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Article Information

Corresponding Author: Jennifer T. Huang, MD, Dermatology Program, Boston Children's Hospital, Department of Dermatology, Harvard Medical School, Fegan Six, 300 Longwood Ave, Boston, MA 02446 (jennifer.huang@childrens.harvard.edu).

Conflict of Interest Disclosures: None reported.

Additional Contributions: We thank the patient’s parents for granting permission to publish this information.

References
1.
Miller  RA.  Maculae ceruleae.  Int J Dermatol. 1986;25(6):383-384.PubMedGoogle ScholarCrossref
2.
Tsoureli-Nikita  E, Campanile  G, Hautmann  G, Hercogova  J. Pediculosis. In: Katsambas  AD, Lotti  TM, eds.  European Handbook of Dermatological Treatments. 2nd ed. Berlin, Germany: Springer; 2003:775-779.
3.
Ko  CJ, Elston  DM.  Pediculosis.  J Am Acad Dermatol. 2004;50(1):1-12.PubMedGoogle ScholarCrossref
4.
Safdi  SA, Farrington  J.  Constitutional reactions and maculae ceruleae attending phthiriasis pubis.  Am J Med Sci. 1947;214(3):308-311.PubMedGoogle ScholarCrossref
5.
Dadabhoy  I, Butts  JF.  Parasitic skin infections for primary care physicians.  Prim Care. 2015;42(4):661-675.PubMedGoogle ScholarCrossref
6.
Ragosta  K.  Pediculosis masquerades as child abuse.  Pediatr Emerg Care. 1989;5(4):253-254.PubMedGoogle ScholarCrossref
7.
Flinders  DC, De Schweinitz  P.  Pediculosis and scabies.  Am Fam Physician. 2004;69(2):341-348.PubMedGoogle Scholar
8.
Chosidow  O.  Scabies and pediculosis.  Lancet. 2000;355(9206):819-826.PubMedGoogle ScholarCrossref
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