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Answer: Factor IXDeficiency of factor IX causes

Christmas disease, or hemophilia B. Theoriginal mutation was identified in 1952by sequencing the DNA of a young boynamed Stephen Christmas, who was foundto be lacking this factor. Recombinant fac-tor IX is used to treat Christmas disease,and a formulation is commercially avail-able. (Source: http://en.wikipedia.org/wiki/Factor_IX).

Bonus clue: Find another holiday-relat-ed item (minus an “E”) in the verticalcolumns. A

C R O S S E D W O R D S

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B A F F L E D

S T A R T L E

A R C U A T EM U T I S M S

S C O T O M A

S A R C O I D

S C I A T I C

S I X K I L O

Answer and critiqueThe correct answer is D: Transvaginal

ultrasound. This question can be found inMKSAP 16 in the Dermatology section,item 40.

The most appropriate diagnostic studyfor this patient is a transvaginal ultrasound.It is likely that this patient has amyopathicdermatomyositis, a condition characterizedby the typical rash and histologic findingsof dermatomyositis but in the absence ofclinical myopathy. In these patients, as wellas in patients with classic dermatomyositis,ovarian cancers are overrepresented, andthese patients should be evaluated with

appropriate imaging. Patients with der-matomyositis and cutaneous ulcerationsmay be at an even higher risk of malignan-cy. Given this patient’s symptoms ofincreasing abdominal girth, along with herfamily history, ovarian cancer is a reason-able concern.

Antinuclear antibody (ANA) serologictesting may be useful in the diagnosisof autoimmune diseases and is frequentlypositive in dermatomyositis. A negativeANA, however, would not exclude adiagnosis of dermatomyositis, and ANAstatus would not alter the evaluation ormanagement of this patient.

Carcinoembryonic antigen is a non-specific tumor marker that may be elevatedin the presence of colon cancer, as well asother tumors such as pancreatic, gastric,lung, and breast; it is an inadequate screen-ing and diagnostic test. The CA 19-9 levelis elevated in subsets of colon, gastric, andpancreatic tumors. Neither is likely to helpidentify the most likely diagnosis in thispatient.

Thigh muscle biopsy is not indicatedin this patient. Dermatomyositis may bediagnosed without muscle inflammationin patients with amyopathic dermato-myositis or those with minimal muscle

disease, known as hypomyopathic der-matomyositis. A blind muscle biopsy islow yield. If the patient were havingsymptoms of muscle pain or weakness, amuscle biopsy would be indicated. Thepresence of a negative electromyogram,normal serum aminotransferase levels,and normal creatine kinase and aldolaselevels make active muscle inflammationunlikely.

Key point■ All patients with a new diagnosis

of dermatomyositis should undergo age-and sex-appropriate cancer screening. A

T E S T Y O U R S E L F

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