The Dermatologist’s Board Review - February 2020

The contents of these questions are taken from the Galderma Pre-Board Webinar. The Pre-Board Webinar is now an online course. For details, go to https://www.galdermausa.com/Our-Commitment/PreBoard-Webinar.aspx.

1. Small periungual papules with increased longitudinal nail ridging are pathognomonic of which one of the following disorders:

a) Granuloma annulare
b) Pseudolymphoma
c) Sarcoid
d) Multicentric reticulohistiocytosis
e) Xanthoma disseminatum

2. The most likely diagnosis is:

a) Melanoma
b) A lesion of the distal matrix
c) A methicillin-resistant Staphylococcus aureus (MRSA) paronychia
d) A myxoid cyst
e) Candida paronychia

1. Small periungual papules with increased longitudinal nail ridging are pathognomonic of which one of the following disorders:

d) Multicentric reticulohistiocytosis

Periungual papules are a singular sign of multicentric reticulohistiocytosis or lipoid dermatoarthritis. This condition is a paraneoplastic disorder that has been reported to occur in association with lung, breast, and gastrointestinal cancers, among others. Granuloma annulare and pseudolymphoma do not involve the nails. Sarcoid shows small papular lesions but they are rarely periungual. Generalized yellowish to orange papules are noted in xanthoma disseminatum, however, they have no particular predilection for the nail unit.

References
Kamata Y, Minota S. Progressive multicentric reticulohistocytosis. Intern Med. 2012;51(6):687-688.
doi:10.2169/internalmedicine.51.6827
Levine D, Miller S, Al-Dawsari N, Barak O, Gottlieb AB. Paraneoplastic dermatoses associated with gynecologic and breast malignancies. Obstet Gynecol Surv. 2010;65(7):455-461. doi:10.1097/OGX.0b013e3181efb12a
Kaul A, Tolat SN, Belgaumkar V, Mhaske CB. Multicentric reticulohistiocytosis. Indian J Dermatol Venereol Leprol. 2010;76(4):404-407. doi:10.4103/0378-6323.66598

2. The most likely diagnosis is:

d) A myxoid cyst

This is not a case of nail melanoma. There is no longitudinal melanonychia nor any sign of pigmentation. Although there is a paronychia present in the generic sense, it is focal, unlikely in Candida infection, and noninflamed, which would be expected in a bacterial (MRSA) infection. The lesion involves the proximal matrix, thus the longitudinal groove of the nail plate. It is the most common cause of longitudinal groove of the nail plate.

References
Simon Cypel TK, Mrad A, Somers G, Zuker RM. Ganglion cyst in children: reviewing treatment and recurrence rates. Can J Plastic Surg. 2011;19(2):53-55. doi:10.1177/229255031101900204
Alam M, Waycha M, Kim-Orden NA, Minkis K. Digital mucous cyst. Medscape. https://emedicine.medscape.com/article/1056917-overview. Published July 31, 2018. Accessed January 20, 2020.