Board Review: In partnership with Derm In-Review

1.)   B.   The correct answer is B. This is a case of Mycoplasma pneumoniae-induced rash and mucositis (MIRM).

The main differential diagnoses include Stevens Johnson syndrome/toxic epidermal necrolysis (C), erythema multiforme (A), herpes simplex infection (A), paraneoplastic pemphigus (D), and less likely Kawasaki disease (E). Patients with MIRM typically have predominantly mucosal involvement (most commonly oral) and absent to sparse cutaneous involvement, which is often vesiculobullous or targetoid when present. It typically has a very good prognosis compared to SJS/TEN and is not caused by medications. CXR may show an atypical pneumonia and there is evidence of a Mycoplasma infection (IgM, PCR, etc.). It is useful to differentiate MIRM (aided by clinical findings and tests as above) from SJS/TEN to avoid unnecessarily aggressive treatment given the better prognosis. If workup for MIRM were negative, it would be prudent to evaluate for paraneoplastic pemphigus (D).

References: Canavan TN, Mathes EF, Frieden I, Shinkai K. Mycoplasma pneumoniae-induced rash and mucositis as a syndrome distinct from Stevens-Johnson syndrome and erythema multiforme: a systematic review. J Am Acad Dermatol. 2015 Feb;72(2):239-45.

2.)   A.   The correct answer is A (A is false).

This is a case of linear IgA bullous dermatosis, a subepidermal vesiculobullous disorder with direct immunofluorescence showing linear IgA deposits at the basement membrane. Clinically, tense bullae can appear annular, herpetiform, or in a linear fashion as a “string of pearls,” as in this case. Antibodies are directed at a 97 kDa antigen near the collagenous domain of BPAg2 (BP180/Collagen XVII), in contrast to the MCW-1 region of the NC16 domain (near transmembrane portion) in other bullous disorders such as bullous pemphigoid (A).

3.)   C.   The correct answer is C (C is false).

Howel-Evans syndrome is an autosomal dominantly inherited disorder with focal palmoplantar keratoderma and squamous esophageal carcinoma. The PPK is typically worse on the soles and over areas of pressure. Abnormalities in hair and teeth have not been reported.