The Bone Morphogenetic Protein (BMP) family reiteratively signals to direct disparate cellular fates throughout embryogenesis. In the developing dorsal spinal cord, multiple BMPs are required to specify sensory interneurons (INs). Previous studies suggested that the BMPs act as concentration-dependent morphogens to direct IN identity, analogous to the manner in which sonic hedgehog patterns the ventral spinal cord. However, it remains unresolved how multiple BMPs would cooperate to establish a unified morphogen gradient. Our studies support an alternative model: BMPs have signal-specific activities directing particular IN fates. Using chicken and mouse models, we show that the identity, not concentration, of the BMP ligand directs distinct dorsal identities. Individual BMPs promote progenitor patterning or neuronal differentiation by their activation of different type I BMP receptors and distinct modulations of the cell cycle. Together, this study shows that a ‘mix and match’ code of BMP signaling results in distinct classes of sensory INs.

No abstract

Ustekinumab (STELARA), a human monoclonal antibody directed against IL‐12 and IL‐23, is FDA‐approved to treat psoriasis, psoriatic arthritis, Crohn's disease, and ulcerative colitis. Increasing recognition of paradoxical skin reactions induced by older biologic therapies used for inflammatory bowel diseases (IBD), such as, adalimumab and infliximab, has led to the investigation of ustekinumab for the treatment of the cutaneous and gastrointestinal manifestations of IBD. In addition, ustekinumab may show efficacy in treating paradoxical cutaneous reactions to tumor necrosis factor‐alpha (TNF‐α) inhibitors. A search of the Medline/PubMed database, with additional citations obtained from the references section of relevant articles, yielded 22 articles that were included in this review. Ustekinumab is a safe and effective option for treating the cutaneous manifestations of IBD, such as, metastatic Crohn's disease and pyoderma gangrenosum. It is also an effective treatment for TNF‐α inhibitor‐induced paradoxical skin reactions, such as, psoriasis that do not remit spontaneously or with conventional treatment. Additional studies should focus on the optimal dosing of ustekinumab for dermatologic conditions beyond psoriasis.

Tyrosine kinase inhibitors are a class of targeted anticancer drugs that inhibit cancer cell proliferation by inactivating proteins involved in signal transduction cascades. Various cutaneous adverse events have been observed after tyrosine kinase inhibitor administration, including Sweet syndrome. We queried the PubMed database to identify 14 cases of Sweet syndrome thought to be secondary to tyrosine kinase inhibitors. Tyrosine kinase inhibitor‐induced Sweet syndrome had a median of 2 months latency following drug administration. All cases but one had morphologic features classic for Sweet syndrome (erythematous and tender papules, plaques, or nodules). All cases also had classic histopathologic findings (dermal neutrophilic infiltrate without vasculitis or necrosis). Using diagnostic criteria for drug‐induced Sweet syndrome and the Naranjo Drug Reaction Probability Scale for a drug‐induced cutaneous eruption, we found that six cases favored a drug‐induced etiology over malignancy, two cases favored a malignancy‐associated Sweet syndrome, and the remaining eight met drug‐induced Sweet syndrome criteria but had low Naranjo scores. Nine cases resulted in medication discontinuation, while five cases continued anticancer therapy and were treated only with corticosteroids with quick resolution of skin lesions. Dermatologists should be aware of this adverse cutaneous reaction to tyrosine kinase inhibitors and should treat on a case‐by‐case basis, though limited evidence in this review suggests that oncologic therapy may safely be continued with prompt corticosteroid treatment.