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Gain-of-function missense mutations of SCN9A gene, which encodes voltage-gated sodium channel Nav1.7, alter channel's biophysical properties causing painful disorders which are refractory to pharmacotherapy in the vast majority of patients. Here we report a novel SCN9A mutation (ca.T3947C) in exon 20 in a 9 year old patient, not present in 200 ethnically-matched control alleles; the mutation substitutes the invariant valine 1316 residue within DIII/S5 by alanine (V1316A). Voltage-clamp studies show that Nav1.7 V1316A mutation hyperpolarizes activation (-9 mV), and enhances response to ramp stimuli (3-fold), changes that are predicted to cause hyperexcitability of DRG neurons. V1316A also hyperpolarizes steady-state slow-inactivation (-9.9 mV), which is predicted to attenuate the effect of this mutation on DRG neuron firing. These changes are consistent with previously characterized Erytheromelalgia associated mutations of Nav1.7., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Erythromelalgia (also termed erythermalgia) is a neuropathic pain syndrome, characterized by severe burning pain combined with redness in the extremities, triggered by mild warmth. The inherited form of erythromelalgia (IEM) has recently been linked to mutations in voltage-gated sodium channel Nav1.7, which is expressed in peripheral nociceptors. Here, we used whole-cell voltage-clamp recordings in HEK293 cells to characterize the IEM mutation L823R, which introduces an additional positive charge into the S4 voltage sensor of domain II. The L823R mutation produces an approximately 15mV hyperpolarizing shift in the midpoint of activation and also affects the activation slope factor. Closing of the channel from the open state (deactivation) is slowed, increasing the likelihood of the channel remaining in the open state. The L823R mutation induces a approximately 10mV hyperpolarizing shift in fast-inactivation. L823R is the only naturally-occurring IEM mutation studied thus far to shift fast-inactivation to more negative potentials. We conclude that introduction of an additional charge into the S4 segment of domain II of Nav1.7 leads to a pronounced hyperpolarizing shift of activation, a change that is expected to increase nociceptor excitability despite the hyperpolarizing shift in fast-inactivation, which is unique among the IEM mutations.

Human mast cell precursors arise in the bone marrow and circulate to different tissue microenvironments, where they develop distinct phenotypes that may be characterized by differential expression of the serine protease, chymase. The growth and development of mast cells is stimulated by mast cell growth factor, which is also known as kit ligand because its obligate receptor is KIT, the protein product of the c-KIT proto-oncogene. The in vivo influence of the KIT-kit ligand axis on the phenotype of human mast cells has not been determined. We used immunohistochemistry to detect in situ expression of tryptase and chymase by mast cells of a patient with urticaria pigmentosa and aggressive systemic mastocytosis, whose pathologic mast cells are clonally derived and chronically stimulated by KIT because they all contain the same point mutation causing constitutive activation of KIT. Mast cells in both spleen and skin expressed tryptase, but only in the skin did a majority of mast cells express chymase. We conclude that chronic stimulation of the KIT-kit ligand axis does not irrevocably commit mast cells to a chymase-positive or chymase-negative phenotype. These findings suggest that factors other than kit ligand predominate in determining mast cell phenotype.

Cutaneous T-cell lymphoma (CTCL) is a malignancy of mature T lymphocytes, most of which express alpha/beta type T-cell receptors (TCRs). The cause of CTCL is unknown, but hypotheses postulating chronic stimulation of TCRs by superantigen or by a leukemogenic virus have been proposed. Either mechanism might produce bias in the TCR variable (V) region types used by the malignant cells. To determine if TCR alpha use is restricted in CTCL, we used reverse transcription and the polymerase chain reaction to determine V alpha and V beta usage by malignant cells purified from the peripheral blood of leukemic patients with CTCL. Usage of alpha chain V region segments appeared totally random; malignant lymphocytes isolated from each of six patients used different V alpha regions. As has been previously reported, no bias was found in beta chain V region usage either. In addition to productive (in frame) TCR V region mRNAs in malignant cells from each patient, we detected non-productive (out of frame) beta chain transcripts in these cells in two of six patients, and non-productive alpha chain transcripts in five of six. Residual normal peripheral blood lymphocytes from these patients showed a random, polyclonal or oligoclonal pattern of V region usage. We conclude that there is no bias in V region usage in CTCL, making it unlikely that interactions between superantigen or virus and the TCR V regions play a role in the pathogenesis of CTCL.

A study of the effects of oral acyclovir (200 mg), administered five times per day for 5 days in 210 patients who cultured positive for herpes labialis, is made. A total of 149 patients were followed through three episodes each of herpes labialis while taking a placebo or acyclovir. Patients were evaluated for several clinical parameters, including the loss of lesion crust and reduction of the size of the area of the lesion between day 1 and day 5. Acyclovir showed a significant antiviral effect. Results show that oral acyclovir can favorably affect some parameters, but that higher doses or a "loading dose" could improve its efficacy.