The correct diagnosis is Darier disease (choice “d”).
Darier disease, also known as Darier-White disease or keratosis follicularis, is an inherited defect transmitted by autosomal dominant mode. The pathophysiologic process is a breakdown of cell adhesion that normally binds keratin filaments to tiny connecting fibers called desmosomes.
Darier disease manifests with a “branny” papulosquamous rash, typically arising in the third decade of life and affecting the chest, scalp, back, and intertriginous areas. The nail and intraoral findings noted in this patient are typical. In the author’s experience, the former is more commonly seen and is essentially pathognomic for the disease.
Darier disease is relatively rare, occurring in 1:30,000 to 1:100,000 population, depending on the geographic area studied. Men and women are equally affected, although it is more common in those with darker skin.
The differential outlined in the answer choices is reasonable, considering the condition’s rarity and how unlikely it is to manifest solely in the inframammary area. One could conclude that, just as with psoriasis (choice “b”) and seborrhea, intertrigo (choice “c”) is not always a primary process. And although yeast infection (choice “a”) can complicate any florid rash in this area, topical and oral anti-yeast treatment had utterly failed to help.
Isotretinoin is used in cases such as this one, but it only offers temporary relief. For less severe cases, oral antibiotics (eg minocycline) or topical steroids (used with caution given the risk for atrophy in the inframammary area) often suffice. This patient’s prognosis is guarded at best, although control of the worst is certainly possible.