A. Malignant atrophic papulosis
The differential diagnoses to consider in a patient who has cutaneous papules and myelopathy can include infectious (eg, secondary syphilis, HIV), ischemic (eg, malignant atrophic papulosis), autoimmune (eg, systemic lupus erythematosus, Behçet disease), and paraneoplastic (eg, scleromyxedema with paraproteinemia) causes.
The diagnosis of malignant atrophic papulosis (MAP) or Köhlmeier-Degos disease was supported by the characteristic cutaneous eruption and histological findings of wedge-shaped dermal collagen degeneration, interstitial mucin deposition, small–vessel angiopathy with luminal thrombi, perivascular and perineural lymphocytic infiltration, and interface vacuolar alteration of the epidermis (Figure 2). These findings, indicative of microvascular injury, can also be seen in the setting of Degos-like diseases, namely dermatomyositis, lupus erythematosus, and scleroderma. Negative autoimmune markers and the absence of characteristic clinical features excluded these differential diagnoses. Scleromyxedema is an unusual condition of dermal mucin deposition and fibroblast proliferation and is typically associated with a monoclonal gammopathy and other systemic manifestations. Histopathological findings of microvascular injury in the patient are not consistent with this diagnosis. Lues maligna is a rare but severe form of secondary syphilis that has been described in patients who have HIV co-infection—cutaneous lesions start out as papules that ulcerate to become well-demarcated necrotic plaques. Syphilis was ruled out with negative findings on serum, cerebrospinal fluid treponemal, and nontreponemal antibody tests, and the absence of spirochetes on skin biopsy. The acute and stepwise deterioration of this patient’s thoracic myelopathy is consistent with a vascular event.